|
|
 Previous Article | Table of Contents | Next Article 
Blood, Vol. 93 No. 4 (February 15), 1999:
pp. 1277-1286
CD8 T-Cell Infiltration in Extravascular Tissues of Patients With
Human Immunodeficiency Virus Infection. Interleukin-15 Upmodulates
Costimulatory Pathways Involved in the Antigen-Presenting Cells-T-Cell
Interaction
By
Carlo Agostini,
Renato Zambello,
Monica Facco,
Alessandra Perin,
Francesco Piazza,
Marta Siviero,
Umberto Basso,
Michela Bortolin,
Livio Trentin, and
Gianpietro Semenzato
From Padua University School of Medicine, Department of Clinical and
Experimental Medicine, Padua Hospital, Padua, Italy.
 |
ABSTRACT |
Interleukin (IL)-15 regulates the proliferative activity of the
CD8+ T-cell pool in human immunodeficiency virus
(HIV)-infected patients, thereby contributing to the maintenance of the
CD8+ T-cell-mediated immune response against HIV in
extravascular tissues, including the lung. However, the effects of
IL-15 on antigen-presenting cells (APC) during HIV infection are still unclear. In this study, we evaluated whether IL-15 regulates the macrophage stimulatory pathways governing inflammatory events that take
place in the lung of patients with HIV infection. As a first step we
evaluated the in vitro effects of IL-15 on lung macrophages retrieved
from the respiratory tract of eight normal subjects. Although
macrophages from uninfected individuals expressed the IL-15 binding
proteins (IL-15R and the common  c) at resting conditions, they
did not express IL-15 messenger RNA (mRNA). However, a 24-hour
stimulation with IL-15 induced the expression of interferon- (IFN-) and IL-15 itself, suggesting a role for this cytokine in the
activation of the pulmonary macrophage pool during inflammation. As a
confirmation of the role of IL-15 in this setting, at resting conditions, alveolar macrophages of patients with HIV infection and
T-cell alveolitis expressed IL-15, IFN-, and IL-15 binding proteins;
showed an upmodulation of costimulatory molecules, B7 and CD72, which
are involved in the APC of macrophages; and behaved as effective
accessory cells because they elicited a strong proliferation of T
cells. The accessory effect was inhibited by pretreatment with
anti-CD72, anti-B7 (CD80 and CD86), and anti-IL-15 monoclonal antibodies (MoAb). We then investigated the relationship between IL-15
and the expression of costimulatory molecules by macrophages. A 24-hour
stimulation of IL-15R+/c+ macrophages
with IL-15 upregulated the expression of CD80 and CD86. The evidence
that IL-15 upregulates the expression of coligands that favor the
contact between T cells and APC, per se, triggers T-cell activation and
proliferation and acts as a chemoattractant for T cells, suggests that
IL-15 plays a key role in Tc1-mediated defense mechanisms taking place
in extravascular tissues of patients with HIV disease.
© 1999 by The American Society of Hematology.
| |
INTRODUCTION |
SEVERAL STUDIES HAVE shown the spread of
human immunodeficiency virus (HIV) to the extravascular tissues and the
appearance of local HIV-specific immune responses that attempt to
eradicate the virus from the involved organs.1 Indeed, in
striking contrast to the peripheral and tissue CD4 lymphopenia, HIV
may cause a marked CD8+ T-cell infiltration in different
tissues, including the lung, lymph nodes, liver, salivary glands,
kidney, and bone marrow.2 We recently suggested that tissue
macrophages are not bystander cells in this phenomenon, because they
actively release mediators of inflammation that lead to the local
activation and expansion of the cytotoxic T-lymphocyte (CTL) pool in
organs affected by HIV infection.3 In particular, when a
starvation of interleukin (IL)-2 occurs as a consequence of a
progressive, quantitative impairment of CD4+ T cells, IL-15
plays a critical role in the CD8+ T-cell
compartmentalization. For instance, in the lung IL-15 induces the
proliferation of oligoclonal CD8+ CTL involved
in the clearance of HIV-infected T cells within the alveolar
space.4-6
The interaction between antigen-presenting cells (APC) and T cells is a
critical factor in initiating the in loco T-cell activation and
proliferation. Furthermore, the outcome of the interaction of a T cell
with an APC on T-cell proliferation depends on the presence of a number
of costimulatory molecules on the APC, including members of the B7
family (CD80 and CD86), some molecules of the tumor necrosis factor
(TNF)-receptor superfamily (CD40 and CD27), and the CD5 coligand
CD72.7,8 To investigate the molecular mechanisms governing
IL-15-mediated activation of the CD8+ T-cell-mediated
immune response we evaluated whether IL-15 modulates the expression of
these costimulatory molecules in an extravascular tissue that is a
common site of CD8+ T-cell infiltration, ie, the lung. Our
results show that alveolar macrophages (AM) of HIV-infected patients
express IL-15 and its receptor structure. In addition, IL-15
consistently upregulates the expression of costimulatory molecules
involved in the APC/T-cell contact, the expression of cytokines
involved in the accessory function of macrophages, and the
proliferative activity of lung T cells that in most of our patients
show a Tc1 cytokine pattern.
| |
MATERIALS AND METHODS |
Study populations.
Fourteen HIV-1 seropositive patients were analyzed (10 men and 4 women;
average age 33.2 ± 4.1 years; risk category for HIV infection was
high-risk heterosexual contact in 5 patients and intravenous drug use
in 9 patients). At the time of the bronchoalveolar lavage (BAL)
evaluation each patient underwent history, physical examination, and
routine blood studies; HIV seropositivity was confirmed by both
enzyme-linked immunoassay and Western blot analysis. According to the
Centers for Disease Control (CDC) classification, 5 previously
asymptomatic patients who during their follow-up showed clinical
symptoms and signs of HIV infection other than, or in addition to
lymphoadenopathy were reclassified in category B; they were all
antiretroviral naive at the time of the BAL evaluation. Nine patients
were classified in category C; 8 of these subjects had previously
received therapy with zidovudine. In all patients, BAL was performed to
obtain a specific diagnosis of opportunistic infections according to
our study protocol for HIV patients with suspected pulmonary
involvement.9 BAL samples were submitted for cytological
studies, stained for Pneumocystis carinii, and stained and
cultured for mycobacteria and fungi.9 On the basis of BAL
analysis an opportunistic pulmonary infection (a Pneumocystis carinii pneumonia) was shown in 9 of the 14 patients.
Immunologic studies were restricted to HIV-seropositive selected
patients in whom complete morphological and immunological analyses of
BAL cellular components were available, including cell recovery,
differential count of macrophages, lymphocytes, neutrophils, and
eosinophils, and flow cytometry analysis of CD3, CD4, and CD8 BAL
T-cell populations (Table 1). Patients
included in the study had minimal prerequisite lung function status and arterial blood gases to minimize the risk factor for the development of
adverse effects with BAL, a platelet count greater than 20,000/mL, and
a prothrombin time greater than 50%.9 BAL specimens
obtained from three HIV-infected patients with lymphocytic alveolitis
were excluded from the study due to blood cell contamination of BAL specimens.
View this table:
[in this window]
[in a new window]
|
Table 1.
Summary of Cell Findings in Bronchoalveolar Lavage of 14 Patients With HIV Infection and CD8+ T-Cell
Alveolitis
|
|
Eight healthy adult controls were selected (five men and three women;
average age 29.7 ± 5.9 years; three nonsmoking healthy persons and
five subjects evaluated for complaints of cough without lung disease).
They showed normal physical examinations, chest X-rays, lung function
tests, and BAL cell numbers.
Preparation of cell suspensions.
The BAL was performed according to the technical recommendations and
guidelines for the standardization of BAL procedures previously
reported.10 Briefly, a total of 200 to 250 mL of saline
solution was injected in 25 mL aliquots via fiberoptic bronchoscopy,
with immediate vacuum aspiration after each aliquot. Immediately after
the BAL, the fluid was filtered through gauze and the volume measured.
A volume of 100 to 200 mL of BAL recovery and a sample of 50% of the
instilled volume with a minimum of 50 mL were considered acceptable.
The percentage of BAL recovery was 56.7% ± 3.4% and 58.1% ± 4.7% of the injected fluid in patients with HIV-1 infection and
control subjects, respectively. Cells recovered from the BAL were
washed three times with phosphate-buffered saline (PBS), resuspended in
endotoxin tested RPMI 1640 (Sigma Chemical Co, St Louis, MO)
supplemented with 20 mmol/L HEPES and L-glutamine, 100 U/mL penicillin,
100 µg/mL streptomycin, and 10% fetal calf serum (FCS; ICN Flow,
Costa Mesa, CA) and then counted. Macrophages, lymphocytes,
neutrophils, and eosinophils were differentially counted in a total
count of 300 cells according to morphological criteria in
cytocentrifuged smears stained with Wright-Giemsa. Peripheral blood
mononuclear cells were harvested from freshly heparinized blood
specimens obtained from five control subjects by centrifugation on
Ficoll-Hypaque (F/H) gradient as previously reported.3
Table 1 reports differential BAL cell counts in patients and controls.
In all normal individuals the total cell recovery ranged from 6.5 to 8 × 106 BAL cells; less than 5% of BAL cells were
lymphocytes. In normal subjects both CD4 helper-related and CD8
cytotoxic/suppressor-related cells were present in approximately the
same proportions as in peripheral blood. In contrast, cell recovery was
significantly higher in patients with HIV infection than in control
subjects. With regard to the differential count of BAL cells,
CD4+ T cells were less than 5% in all BAL specimens; all
patients showed a T-cell alveolitis. As a consequence of the decrease
in the CD4+ T-cell population and the increase in the
absolute number of CD8+ T cells, the BAL CD4/CD8 ratio was
dramatically decreased in all HIV-infected patients (Table 1).
Purification of AM and T cells.
AM were enriched from the BAL cell suspensions by rosetting with
neuraminidase-treated sheep red blood cells (SRBC)
followed by F/H-gradient separations.3 AM were further
enriched by removing residual CD3+, CD16+, and
CD56+ lymphocytes using high-gradient magnetic separation
columns (Mini MACS, Miltenyi Biotec, Germany), as previously
described.3 After this multistep selection procedure more
than 95% of the above cells were viable, as judged by trypan blue
exclusion test. The staining with monoclonal antibodies (MoAb) showed
that more than 98% of BAL cells expressed the AM-associated CD68 antigen.
The cell suspension of peripheral blood mononuclear cells was depleted
of adherent cells by incubation for 45 minutes in plastic Petri dishes
at 37°C in an atmosphere of 95% air and 5% CO2. T cells were enriched from the resulting cell suspensions by rosetting with neuraminidase-treated SRBC followed by F/H-gradient separations, as previously described.3
MoAb.
The commercially available conjugated or unconjugated MoAb used
belonged to the Becton Dickinson (Sunnyvale, CA),
Immunotech (Marseille, France), and PharMingen (San Diego,
CA) series and included: CD3, CD4, CD8, CD28, CD45R0, CD45RA, CD69
(FN50), CD72, CD80 (BB-1/B7-1), CD86 (B70/B7-2), CD152 (CTLA-4), and
HLA-DR and isotype matched controls. Anti-IL-15 M110 (IgG1) and
anti-IL-15 receptor (IL-15R )(IgG1) MoAb were kindly provided by Dr
A. Troutt (Immunex Co, Seattle, WA); anti-TNF- (MAB11), anti-IL-2
(MQ1-17H12), anti-IL-4 (8D4-8), and anti-interferon (IFN)- (4S.B3)
MoAb were purchased from PharMingen. The frequency of BAL cells
positive for the above reagents was determined by overlaying the flow
cytometry histograms of the samples stained with the different reagents as previously described.3 Cells were scored using a FACScan analyzer (Becton Dickinson), and data were processed using the Macintosh CELLQuest software program (Becton Dickinson). The expression of cytoplasmic cytokine was evaluated after permeabilization of cell
membranes using 1:2 diluted PermeaFix (Ortho, Raritan, NJ) for 40 minutes. After permeabilization procedures, anti-IL-15, anti-TNF-,
anti-IFN-, anti-IL-12, and anti-IL-2 MoAbs were added. Because
pulmonary cells bore cytoplasmic cytokine in a unimodal expression
pattern, indicating that the entire cell population exhibits relatively
homogeneous fluorescence, the percentage of positive cells does not
represent the most accurate way of enumerating positive cells. For this
reason, the mean fluorescence intensity (MFI) was used to compare the
positivity of these specific antigens on different cell populations. To
evaluate whether the shift of the positive cell peak was statistically
significant, the Kolmogorov-Smirnov test for analysis of histograms was
used according to the Macintosh CELLQuest software user's guide
(Becton Dickinson).
For immunofluorescence analysis, control IgG1 and IgG2a and IgG2b were
obtained from Becton Dickinson; control rat antiserum consisted of
ascites containing an irrelevant rat IgG2b mAb (kindly provided by A. Rosato, Padova, Italy); control rabbit antiserum consisted of rabbit
IgG myeloma (purified protein) purchased from Serotec (Serotec, UK);
goat-anti-rabbit IgG and goat F(ab')2 anti-rat IgG were obtained from
Immunotech (Marseille, France).
RNA extraction, complementary DNA (cDNA) synthesis and polymerase
chain reaction (PCR) amplification of IFN-,
TNF-, IL-15, and IL-15R complex
(IL-15R, IL-2R ,
IL-2Rc).
Total cellular RNA was extracted using the Ultraspec I RNA isolation
system (Biotecx Lab, Houston, Texas) from unstimulated and IL-15
stimulated AM. cDNAs were prepared from 2 µg of total cellular RNA by
reverse transcription (RT) using a kit from Invitrogen Corp (San Diego, CA).
For the amplification of IFN-, TNF-, IL-15, -actin, and IL-15R
complex, PCR was conducted in a 50 µL reaction using 2 µL of cDNA
as template. The PCR mixture consisted of 1.5 mmol/L MgCl2, 50 mmol/l KCL, 10 mmol/l Tris-HCl, 0.2 mM/L concentrations of each
deoxynucleotide triphosphate, 2.5 U of Taq polymerase (Perkin Elmer,
Norwalk, CT) and 25 pmol/L of each specific primer. The following sense
and antisense oligonucleotide primer sequences were used: for IFN-:
5'-AgT TAT ATC TTg gCT TTT CA, 3'-ACC gAA TAA TTA gTC AgC
TT (expected size of 355 bp); for TNF-: 5'-TCT CgA ACC CCg AgT
gAC AA, 3'-TAT CTC TCA gCT CCA CAC CA (expected size of 124 bp);
for IL-15: 5'-CTC gTC TAg AgC CAA CTg ggT gAA TgT AAT AAg,
3'-TAC TTA CTC gAg gAA TCA ATT gCA ATC AAg AAg Tg (expected size
of 404 bp); for -actin: 5'-gTg ggg CgC CCC Agg CAC CA,
3'-CTC CTT AAT gTC ACg CAC gAT TTC (expected size of 540 bp); for
IL-15R: 5'-ggC gAC gCg ggg CAT CAC, 3'-TCg CTg Tgg CCC TgT ggA TA (expected size of 531 and 432 bp); for IL-2R:
5'-TAT Agg ATC CgA AgA gCA AgC gCC ATg TTg AAg CC, 3'-AgA
TTC TgC AgT TTT AgC ATC TgT gTg gCC (expected size of 451 bp). IL-2R
was amplified using the human IL-2 receptor subunit kit (Clontech, Palo Alto, CA).
IFN-, TNF-, and IL-2Rc were amplified at the
following conditions: 60 seconds melting at 94°C, 45 seconds
annealing at 53°C for IFN- and 58°C for TNF- and 120 seconds extension at 72°C for 35 cycles followed by a final
extension for 7 minutes at 72°C in a Cetus/Perkin Elmer thermal
cycler (Emeryville, CA). IL-15 was amplified at the
following conditions: 30 seconds melting at 94°C, 30 seconds
annealing at 55°C and 30 seconds extension at 72°C for 30 cycles followed by a final extension for 7 minutes at 72°C in a
Cetus/Perkin Elmer thermal cycler. IL-15R was amplified at the
following conditions: 30 seconds melting at 94°C, 45 seconds annealing at 62°C and 45 seconds extension at 72°C for 30 cycles followed by a final extension for 7 minutes at 72°C in a
Cetus/Perkin Elmer thermal cycler.
For -actin amplification conditions were 60 seconds melting at
94°C, 60 seconds annealing at 55°C and 120 seconds extension at
72°C for 30 cycles followed by a final extension for 7 minutes at
72°C. 10 µL of each PCR product was electrophoresed in a 2% agarose gel in Tris borate/EDTA buffer. Gels were stained with ethidium
bromide and photographed.
Effect of IL-15 and other locally released cytokines on the
expression of costimulatory molecules by pulmonary macrophages.
To assess the effects of IL-15 on macrophage activation, a time-course
experiment of the effects of cytokines on the expression of CD72, CD80,
and CD86 by AM was performed. AM at the concentration of 1 × 106 cells/mL were cultured in 24-well plates (Corning, New
York, NY) for 24 hours at 37°C in 5% CO2 atmosphere.
After 24 hours of incubation, plates were centrifuged and, after
removal of supernatants, BAL cells were further cultured for 12 hours
with medium alone, with IL-15 (100 ng/mL), or with IL-15 (100 ng/mL)
and IFN- (100 UI/mL). The frequency of BAL cells positive for the
above reagents was determined by flow cytometry, as described above. In
particular, mean log fluorescence intensity (MFI) was obtained by
subtracting the MFI of isotype control from the MFI of the positively
stained sample. In this way, the values of MFI represent the relative increase in fluorescence over the background value reported as zero.
Furthermore, to evaluate whether the differences between the peaks of
cells were statistically significant with respect to controls, the
Kolmogorov-Smirnov test for analysis of histograms was used, according
to the CellQuest software user's guide (Becton Dickinson).
Effect of IL-15 on the expression of cytokines by pulmonary
macrophages.
We also evaluated whether IL-15 may induce IFN- expression on AM.
The cytokine expression was evaluated by PCR analysis and by flow
cytometry after permeabilization of cell membranes, as reported in
detail above.
Evaluation of the involvement of costimulatory molecules in the
accessory function of pulmonary macrophages.
Highly purified T cells at the concentration of 1 × 106 cells/mL were cultured in 96 round-bottom well plates
for 72 hours at 37°C in 5% CO2 atmosphere with 12.5 × 103 AM in the presence of mitogens (ConA; 10 µg/mL, Sigma Chemical Co) as previously reported.3 In
inhibition experiments, anti-CD80 (10 µg/mL), anti-CD86 (10 µg/mL)
and anti-CD72 (20 µg/mL), anti-IL-15 (100 ng/mL) or control
isotype-matched IgG1 were added at the beginning of the
culture. Each experiment was carried out in quadruplicate. For the last
18 hours of culture, plates were pulsed with 1 µCi/well of
(3H)thymidine (Dupont, Bruxelles, Belgium), as reported
above.3
Statistical analysis.
Data were analyzed with the assistance of the Statistical Analysis
System. Data are expressed as mean ±SD. Values were
compared using the Anova test and the Spearman correlation test. A
P value less than .05 was considered as significant.
| |
RESULTS |
The results of differential BAL cell counts and T-cell subpopulations
retrieved from the lung of healthy patients and patients with HIV
infection (Table 1) showed the presence of a discrete alveolitis. With
regard to the differential count of BAL cells, the absolute number of
lymphocytes and AM was significantly increased in patients with HIV
infection with respect to control subjects (P < .001 and .01, respectively). Further characterization of lung lymphocytes showed that
the alveolar lymphocytosis was sustained by CD8+ T cells.
As a consequence of the marked increase in CD8+ T cells,
the pulmonary CD4/CD8 ratio was significantly lower in HIV-infected
patients than in controls (P < .001).
Pulmonary macrophages from uninfected individuals express IL-15
binding proteins, and IL-15 stimulation induces cytokine expression.
As a first step we evaluated the expression of IL-15 receptor on AM
from healthy subjects. Figure 1 shows data
from a representative subject, but consistent data were obtained in six
normal subjects. At resting conditions AM from normal subjects
expressed the IL-15R and the c of the IL-2R, ie, the main
molecules involved in the binding of IL-15. However, unstimulated AM
from five normal subjects (Fig 2) did not
express IFN- or IL-15, two cytokines which have been involved in
local immune responses during interstitial lung disease; however, after
a 24-hour stimulation, IL-15 was able to induce a strong expression of
both cytokines (Fig 2). Concerning TNF-, unstimulated AM expressed
TNF- messenger RNA (mRNA), but after incubation with IL-15, TNF-
signals significantly increased. In fact, in five consecutive normal
subjects the optical density (OD) ratio of mRNA TNF-/actin was
29.131 + 1.027 and 34.929 ± 1.866 in unstimulated AM and
IL-15-stimulated AM, respectively (P < .02). These data
suggest the putative role of IL-15 in the activation of the pulmonary
macrophage pool.
View larger version (37K):
[in this window]
[in a new window]
| Fig 1.
RT-PCR analysis and flow cytometry profile of the
expression of IL-15R, IL-2R, and the c by AM. The
figure shows a representative healthy subject (subject #4) but a
consistent pattern of expression was observed in six consecutively
examined normal subjects. 94% of BAL cells of subject #4 were alveolar
macrophages and 7% lymphocytes, as determined by morphological
evaluation; the CD4/CD8 ratio was 1.9. AM were enriched as reported in
the Materials and Methods section. AM bore high levels of IL-15R and
c whereas a faint expression of IL-2R is
detectable.
|
|
View larger version (42K):
[in this window]
[in a new window]
| Fig 2.
RT-PCR analysis of the expression of the messages for
IL-15, TNF-, and IFN- by AM of a representative healthy subject
cultured for 24 hours in medium alone and in the presence of IL-15. The
figure shows a representative healthy subject (subject #2) but a
consistent pattern of expression was observed in five consecutively
examined normal subjects. 96% of BAL cells of subject #2 were alveolar
macrophages and 4% lymphocytes, as determined by morphological
evaluation and the CD4/CD8 ratio was 2.1. AM were enriched as reported
in the Materials and Methods section.
|
|
BAL cells from patients with HIV infection are preactivated cells
showing spontaneous expression of cytokines and an up-modulation of
costimulatory molecules.
Profiles shown in Figures 3 and
4 are representative of 14 HIV-infected
patients with T-cell alveolitis and 6 uninfected, normal subjects. AM
retrieved from patients with HIV infection and CD8+ T-cell
alveolitis showed an up-modulation of costimulatory molecules, including members of the B7 family and the CD72 molecule (Fig 3, panels
A, B, and C). Interestingly, the expression of CD72, CD80,
CD86 by AM was associated with an increased cell surface density of
activation antigens (Fig 3, panels D, E, and F) and cytokines,
including IL-15, TNF-, and IFN- (Fig 3, panels G, H, and I). As
shown in Fig 5, the B7-2 molecule was found
to be expressed at higher intensity than B7-1 by AM from patients with HIV infection; furthermore, there was an association between the expression of IL-15, the MFI of B7 family members and the degree of
T-cell infiltration in the pulmonary tract. Taken together these data
suggest that AM from patients with HIV infection are in an activation
state with respect to normal AM. In fact, AM from normal subjects did
not bear CD72, CD80, or CD86 (Fig 3, panels J, K, and L); less than 5%
of normal AM were CD14+ (Fig 3, panel M). In addition,
pulmonary macrophages from healthy subjects did not show membrane or
cytoplasmic IL-15 expression (Fig 3, panel P) and less than 5% of
mononuclear phagocytes isolated from the lung of healthy individuals
showed cytoplasmic TNF- (Fig 3, panel Q).
View larger version (32K):
[in this window]
[in a new window]
| Fig 3.
The flow cytometry profile of AM recovered from a
representative HIV-infected patient with lymphocytic alveolitis (case
#5) and an uninfected control subject. BAL analysis revealed the
presence of a P. carinii pneumonia; 34% of BAL cells were
lymphocytes, as determined by morphological evaluation and the CD4/CD8
ratio was 0.03. The profile of CD72, CD80, and CD86 molecules (panels
A, B, C, J, K, and L), activation markers (panels D, E, F, M, N, and
O), and cytoplasmic cytokines (panels G, H, I, P, Q, and R) was
determined as reported in the Materials and Methods section. A
consistent pattern of expression of costimulatory molecules and
cytoplasmic cytokines was observed in all HIV-infected patients with
lymphocytic alveolitis.
|
|
View larger version (30K):
[in this window]
[in a new window]
| Fig 4.
The flow cytometry profile of BAL T cells recovered from a
representative HIV-infected patient with lymphocytic alveolitis (case
#5) and an uninfected control subject. Main results of BAL analysis of
case #5 are summarized in the legend of Fig 3. The profile of CD5,
CD28, and CD152 molecules (panels A, B, C, J, K, and L), activation
markers (panels D, E, F, M, N, and O), and cytoplasmic cytokines
(panels G, H, I, P, Q, and R) was determined as reported in the
Materials and Methods section. A consistent pattern of expression of
costimulatory molecules and cytoplasmic cytokines was seen in all
HIV-infected patients with lymphocytic alveolitis.
|
|
View larger version (23K):
[in this window]
[in a new window]
| Fig 5.
RT-PCR analysis of the expression of the messages for
IL-15 and mean fluorescence intensity values of IL-15, CD80, and CD86
histograms shown by AM recovered from two patients with HIV infection.
Specifically, case #6 was a symptomatic patient with AIDS-related
complex whereas case #8 had full-blown AIDS (P. carinii
pneumonia). The percentages of lymphocytes detected in the BAL are
indicated on the right side of the fig. There was a strict association
between the expression of IL-15, the MFI of IL-15, and B7 family
members and the degree of T-cell infiltration, determined on the basis
of BAL lymphocytes percentage. MFI 1: mean fluorescence intensity of
control histogram; MFI 2: mean fluorescence intensity of CD80
histogram; MFI 3: mean fluorescence intensity of CD86 histogram.
|
|
As reported in Table 1, T cells were markedly increased in the lung of
patients with HIV infection. Flow cytometry analysis of BAL T
lymphocytes showed that the alveolar lymphocytosis was sustained by
CD8+/CD45R0+ T cells bearing CD5 and expressing
CD28 molecules at high intensity but lacking CTLA-4 expression (Fig 4,
panels A, B, and C, respectively). We also evaluated the activation
state and the pattern of cytokine production by pulmonary CD8 T cells.
In 11 out of the 14 HIV-infected patients most T cells accounting for
the CD8 alveolitis were preactivated cells (Fig 4, panels D, E, and F)
IFN-+ (Fig 4, panel H) but did not express IL-2 or IL-4
(Fig 4, panels G and I, respectively), a pattern which has been
reported to be characteristic of Tc1 cells.11 In 3 patients
CD8 T cells did not express cytoplasmic cytokines. Normal BAL T cells
expressed CD5 antigen, and a percentage of lung lymphocytes ranging
between 25.3% and 41.5% bore the CD28 molecule but not the CTLA-4
antigen (Fig 4, panels K and L, respectively); furthermore they did not express cytoplasmic cytokines (Fig 4, panels P, Q, and R).
IL-15 upregulates B7 family member expression on local APC.
Our phenotypic data showed that AM cells express IL-15, which is
involved in the induction of T-cell inflammation in peripheral tissues,
including the lung,3 and express a complete IL-15R complex.
Because a number of cytokines are capable of regulating B7 family
expression leading to APC activation, in a time-course experiment we
evaluated whether soluble factors locally produced by AM (ie, IL-15,
TNF-, and IFN-) and T cells (IL-2 and IFN-) may modulate the
expression of CD72, CD80, and CD86 ligands on highly purified AM from
the lung of four patients with HIV infection. Table 2 shows the MFI values of CD72, CD80,
and CD86 tested in the presence of medium and different cytokines. All
the molecules under study showed a unimodal expression on cell surface,
and the histogram was shifted to the right in relation to the intensity of antigen expression.
View this table:
[in this window]
[in a new window]
|
Table 2.
Mean Fluorescence Intensity (MFI) Values of CD80, CD86,
and CD72 Histograms on AM and CD28 and CD152 Histograms on BAL T
Cells in a Time Course Evaluation Test
|
|
Preliminary time course experiments showed that, after 24 to 36 hours
of culture, unstimulated AM partially lose the expression of these
costimulatory molecules (Table 2). Furthermore, the expression of
activation markers and cytoplasmic cytokines by AM progressively drops
in the absence of stimulation (data not shown). The progressive loss of
the activation state was reversed by incubation with IL-15, because
exposure to the cytokine reinduced the expression of B7 molecules on AM
retrieved from the lung of HIV infected patients. As shown by the
comparison of MFI levels, after IL-15 stimulation, AM showed enhanced
levels of CD80 and CD86 expression with respect to the paired samples
of medium-cultured AM (P < .001 as determined by the
Kolmogorov-Smirnov analysis). Incubation with IFN- showed similar
effects on B7 family member expression, whereas neither TNF- nor
IL-2 influenced the expression of accessory receptors. Furthermore,
cytokine stimulation did not or only slightly influenced CD72
expression on AM (data not shown).
A similar phenomenon was observed by restimulating BAL T cells with the
above cytokines (Table 2). Incubation with IL-15 and IFN- and, in
some cases, with IL-2 enhanced the expression of CD28 on 36-hour
cultured lung T cells. The Kolmogorov-Smirnov analysis showed that
histograms of T cells cultured in a cytokine milieu were shifted with
respect to histograms of unstimulated lymphocytes. TNF- did not
modify the expression of CD28. Furthermore, IL-2, IFN- , IL-15, and
TNF- stimulation did not induce CD154 expression.
Costimulatory molecules expressed by pulmonary macrophages following
IL-15 exposure are involved in the regulation of the proliferative
activity of T cells.
The possibility that the increased expression of B7 and CD72 coligands
might account for the in situ proliferation of T cells was also
investigated by an in vitro proliferation assay with highly purified
allogeneic T cells (Fig 6). The purity of
the T-cell populations used in the proliferation assays exceeded 99%, with virtually no detectable residual monocyte-macrophages. Highly purified T cells did not proliferate when stimulated with ConA unless
accessory cells were added. However, T cells without accessory cells
showed a discrete proliferative activity in the presence of 100 ng/mL
of IL-15 (P < .001 with respect to highly purified ConA
stimulated T cells without accessory cells).
View larger version (23K):
[in this window]
[in a new window]
| Fig 6.
The effects of anti-CD80, anti-CD86, and anti-CD72 MoAbs
on accessory function of AM isolated from the BAL of nine patients with
HIV infection (two patients with AIDS-related complex and seven
patients with full-blown AIDS). The above quoted antibodies, when added
to assays at the beginning of culture, significantly inhibited the
mitogen-induced proliferation of highly purified T cells. AM and T
cells were enriched as reported in the Materials and Methods
section.
|
|
Figure 6 also shows that AM induced a proliferation of highly purified
T cells in the presence of mitogen; this data was not surprising given
the known accessory function of pulmonary macrophages from patients
with interstitial lung diseases (ILDs) in mitogen assays.
The blocking effects of CD80 and CD86 MoAbs on the accessory function
of AM are represented. When added to the mitogen assay at the beginning
of culture, anti-CD72, anti-CD80, and anti-CD86 MoAbs inhibited the
proliferation of T cells; there were no statistically significant
differences in the blocking activity of CD80 and CD86 MoAbs, as
determined by thymidine incorporation. The inhibitory ability of a
control MoAb was always less than 2%; as previously reported,3 anti-IL-15 antibodies inhibited the accessory
function of AM (data not shown). These data indicate the functional
importance of the expression of these costimulatory molecules by AM in
inducing both CD4 and CD8 T-cell immune response within the alveolar spaces.
| |
DISCUSSION |
In this study we show that IL-15 upregulates the expression of the
CD72/CD5 and CD80, CD86/CD28 counterreceptors, suggesting a role for
IL-15 in the regulation of costimulatory molecules that favor the APC-T
cell contact and the compartmentalization of the CTL response within
tissues involved by HIV infection.
The lung is a site of compartmentalization of the host immune response
against HIV. In fact, we previously reported that lung involvement in
HIV-infected patients is associated with the intraalveolar accumulation
of CD8+ T cells that are phenotypically different from
those in the peripheral blood12 and sometimes numerous T
cells are still observed locally whereas the patient is severely
lymphopenic in the peripheral blood.9 Mononuclear
phagocytes resident within the lung compartment are not bystander cells
in this phenomenon, because they release a number of factors that favor
the accumulation of T cells.1 In particular, recent
evidence from our laboratory suggests that macrophage-derived IL-15
favors the local cell proliferation in extravascular tissues involved
by HIV infection3; in addition, we found that IL-15 binding
proteins are expressed by pulmonary macrophages of patients with HIV
infection,3 but we did not verify whether IL-15 exerts its
effects on cells of the mononuclear phagocyte system. In this paper we
show that IL-15 is part of the matrix of cytokines that regulates the
accessory activity of AM at sites of inflammatory lesions in the
pulmonary microenvironment. The addition of exogenous IL-15 and IFN-
increased the expression of CD80 and, in particular, CD86 on pulmonary
macrophages. Furthermore, exposure to IL-15 and IFN- augmented the
expression of CD28 on pulmonary CD8 T cells, which in our system were
CD8 Tc cells expressing activation markers and variable levels of
IFN-. In contrast, IL-15 did not influence the expression of the
CD5/CD72 costimulatory pathway. This observation suggests that
additional signals may be important in regulating the accessory
function of AM.
The maturation and expansion of pre-CTL to virus specific CTL occurs
following a complex sequence of cellular interactions and
cytokine-mediated activation signals. After T-cell receptor (TCR)-mediated engagement, costimulatory signals provided by the CD28/B7 interaction induce CTL maturation.13 A number of
cytokines have the potential to regulate the expression of B7/CD28
molecules. CD80 and CD86 are expressed on circulating monocytes after
IFN- activation14,15 whereas IL-10 blocks the expression
of both antigens on peritoneal macrophages and downregulates B7-2
expression on dendritic cells.16 On the other hand, IL-2,
IL-4, TNF-, and IFN- act synergistically to increase CD28
expression.17-19 The present study claims that IL-15 serves
as a potent inducer of an alternative pathway that may regulate B7
expression and thus CTL activation and growth in HIV disease. The
putative regulatory properties of IL-15 in other viral diseases
characterized by a CTL response are currently under investigation in
our lab.
As shown by Kanai et al,20 IL-15 supports the in vitro
generation of effector HIV-env-specific CTL in the absence of
active IL-2. Furthermore, anti-IL-15 MoAb are able to block the
generation and function of virus-specific CTL, suggesting that IL-15
may per se drive the CTL response. In our study, pulmonary
CD4+ T cells were less than 5% in all patients. Because
lung CD4+ T cells are the cell source of IL-2, it is
conceivable that other soluble factors released by AM may surrogate
IL-2 in maintaining the T-cell alveolitis when the number of CD4 T
cells drops. In particular, IL-15, augmenting the set of costimulatory
molecules on APC and signaling CD8+ T cells to proliferate,
might drive the expansion of virus-specific CTL in the absence of
functional CD4+ T lymphocytes.
Infection with HIV results in a generalized immunosuppression. The
functional and quantitative impairment of the Th1 cell population makes
patients with acquired immunodeficiency syndrome (AIDS) susceptible to
opportunistic infections in the respiratory tract. The fact that IL-15
may contribute to the activation and growth of effector T cells not
only against HIV but also against other infectious
agents21-23 suggests an intriguing therapeutic potential
for this cytokine in sustaining the pulmonary immune system in advanced
HIV disease. An optimal host response against opportunists depends on
the local accumulation and activation of effector immunocompetent
cells, two phenomena that in normal subjects are keenly regulated by
IL-2-producing CD4+ Th1 cells. The ability of IL-15 to
enhance CTL and natural killer activity and induce T-cell chemotaxis
might restore the defective Th1-dependent antimicrobial immunity, ie, a
major factor that improves the prognosis in patients with HIV infection
and pulmonary complications.
Because the mechanisms triggering the IL-15 production in the lung are
not known, a major direction for future research will rest on the
definition of molecular events that control IL-15 message translation
in the lung of HIV-infected patients. Pulmonary macrophages are the
first cell type shown to be infected by HIV; in fact, the HIV genome
has been shown in lung macrophages of HIV-infected patients from the
early phases of the disease. Therefore, it might be that HIV or HIV
proteins may per se enhance IL-15 secretion by pulmonary macrophages,
as recently suggested for peripheral blood monocytes.24 An
alternative hypothesis could be that the initial contact between
macrophages with APC and HIV-specific effector pulmonary T cells
represents the event which triggers AM to synthesize IL-15, as
previously reported for dendritic cells.25 It is also
proposed that codependence mechanisms between cytokines that are
locally released during HIV disease could set the stage for the IL-15
hyperproduction. For instance, the T-cell-induced synthesis of IFN-
and TNF- could activate macrophages to synthesize IL-15, which in
turn could induce IFN- and TNF- production, thus generating a
positive feedback loop. IL-10 is another cytokine that might be
relevant in the control of IL-15 production, because recent data
indicate that IL-10 increases IL-15 mRNA.26 In this regard,
we showed that IL-15 stimulation increases IL-10 expression on AM (data
not shown). Non HIV-dependent mechanisms are likely to be equally
important in inducing the production of this mitogenic and chemotactic
factor, notably in patients with opportunistic infections. Because
infection by human intracellular pathogens induces IL-15
expression,21 it is conceivable that IL-15 serves as an
alarm cytokine that is secreted after the infection of macrophages by
the several intracellular microorganisms that colonize the lung during
HIV disease. In this regard, further studies are needed to verify
whether recall antigens from pathogens of the respiratory tract (such
as Pneumocystis carinii) may favor IL-15-dependent proliferation of pulmonary T cells.
In conclusion, this study supports the hypothesis that IL-15
augments T-cell activation in the lung by upregulating the expression of costimulatory ligands on alveolar macrophages. It has been suggested
that the process of activation of pulmonary immune competent cells,
supported by locally released cytokines, may paradoxically contribute
to the spreading of HIV.1 With the advent of triple drug
therapy with two nucleoside analogue reverse transcriptase inhibitors
and a protease inhibitor (highly active antiretroviral therapy, HAART)
it has been possible to obtain an impressive drop in HIV burden and, in
most patients, a downregulation of immune activation of peripheral
blood CD8+ T cells.27 The BAL provides an
opportunity to evaluate the direct effect of HAART therapy on tissues.
In particular, studies should be planned to evaluate whether combined
therapy, which may lead to a reduction of HIV load in the lung (our
preliminary data), is associated with a down- regulation of cytokine
expression, including IL-15, and a return to the normal
CD8+ T-cell activation status in pulmonary tissue.
| |
ACKNOWLEDGMENT |
The authors thank their colleagues from the Departments of Infectious
Diseases and Pulmonary Medicine of the Padua Hospital, in particular
Drs P. Cadrobbi and A. Cipriani, who contributed to this project by
allowing the study of their patients and by performing the
bronchoscopies. We also wish to thank Biogen, Cambridge, MA, for
providing rIL-2; Knoll AG/BASF, Ludwigshafen, FRG, for providing TNF-
; Dr A. Troutt from Immunex Co for providing recombinant IL-15 and
anti-IL-15 M110 MoAb; and Mr Martin Donach for his help in the
preparation of the manuscript.
| |
FOOTNOTES |
Submitted May 8, 1998; accepted October 7, 1998.
Supported by a Grant from the Ministero della Sanità Istituto
Superiore della SanitàProgetto AIDS 1997 (Rome, Italy).
The publication costs of this
article were defrayed in part by
page charge payment. This article
must therefore be hereby marked
"advertisement"
in accordance with 18 U.S.C. section
1734 solely to indicate this fact.
Address correspondence to Gianpietro Semenzato, MD, Università di
Padova, Dipartimento di Medicina Clinica e Sperimentale, Immunologia
Clinica, Via Giustiniani 2, 35128 Padova, Italy.
| |
REFERENCES |
1.
Agostini C, Zambello R, Trentin L, Semenzato G:
HIV and pulmonary immune responses.
Immunol Today
17:359, 1996[Medline]
[Order article via Infotrieve]
2.
Itescu S, Dalton J, Zhang HZ, Winchester R:
Tissue infiltration in a CD8 lymphocytosis syndrome associated with human immunodeficiency virus-1 infection has the phenotypic appearance of an antigenically driven response.
J Clin Invest
91:2216, 1993
3.
Agostini C, Trentin L, Sancetta R, Facco M, Tassinari C, Cerutti A, Bortolin M, Milani A, Siviero M, Zambello R, Semenzato G:
IL-15 triggers activation and growth of the CD8 T-cell pool in extravascular tissues of patients with AIDS.
Blood
89:1115, 1997[Free Full Text]
4.
Plata F, Autran B, Martins LP, Wain-Hobson S, Raphael M, Mayaud C, Denis M, Guillon JM, Debre' P:
AIDS-virus specific cytotoxic T lymphocytes in lung disorders.
Nature
328:348, 1987[Medline]
[Order article via Infotrieve]
5.
Dwyer T, Itescu DS, Winchester R:
Characterization of the primary structure of the T-cell receptor chain in cells infiltrating the salivary gland in the sicca syndrome of HIV-infection: Evidence of an antigen-driven clonal selection suggested by restricted combination of VJ gene segment usage and shared somatically encoded amino acid residues.
J Clin Invest
92:495, 1993
6.
Trentin L, Zambello R, Facco M, Sancetta R, Cerutti A, Milani A, Tassinari C, Crivellaro C, Cipriani A, Agostini C, Semenzato G:
Skewing of the T cell repertoire in the lung of patients with HIV-1 infection.
AIDS
10:729, 1996[Medline]
[Order article via Infotrieve]
7.
Schultze J, Nadler LM, Gribben JG:
B7-mediated costimulation and the immune response.
Blood Rev
10:111, 1996[Medline]
[Order article via Infotrieve]
8.
Flier JS, Underhill LH:
The tumor necrosis factor ligand and receptor families.
N Engl J Med
334:1717, 1996[Free Full Text]
9.
Agostini C, Adami F, Poulter LW, Israel-Biet D, Freitas e Costa M, Cipriani A, Sancetta R, Lipman MCI, Juvin K, Teles-Araujo A, Cadrobbi P, Masarotto G, Semenzato G:
Role of bronchoalveolar lavage in predicting survival of patients with HIV-1 infection.
Am J Respir Crit Care Med
156:1501, 1997[Abstract/Free Full Text]
10.
Costabel U, Danel C, Fabbri ML, Haslam PL, Hutter C, Israel-Biet D, Klech H, Pohl W, Poulter LW, Pozzi E, Rennard SI, De Rose V, Rossi GA, Rust M, Semenzato G, Wallaert B:
Clinical guidelines and indications for bronchoalveolar lavage (BAL): Report of the European Society of Pneumology Task Group on BAL.
Eur Respir J
3:937, 1990[Medline]
[Order article via Infotrieve]
11.
Mosmann TR, Sad S:
The expanding universe of T-cell subsets: Th1, Th2 and more.
Immunol Today
17:138, 1996[Medline]
[Order article via Infotrieve]
12.
Agostini C, Zambello R, Sancetta R, Cerutti A, Milani A, Tassinari C, Facco M, Cipriani A, Trentin L, Semenzato G:
Expression of tumor necrosis factor-receptor superfamily members by lung T lymphocytes in interstitial lung disease.
Am J Respir Crit Care Med
153:1359, 1996[Abstract]
13.
Lenschow DJ, Walunas TH, Bluestone JA:
CD28/B7 system of T cell costimulation.
Annu Rev Immunol
14:235, 1996
14.
Hatchok KS, Laszlo G, Pucillo C, Linsley P, Hodes RJ:
Comparative analysis of B7-1 and B7-2 costimulatory ligands: Expression and function.
J Exp Med
180:631, 1994[Abstract/Free Full Text]
15.
Freedman AS, Freeman GJ, Rhynhart K, Nadler LM:
Selective induction of B7/BB1 on interferon-gamma stimulated monocytes: A potential mechanism for amplification of T cell activation through the CD28 pathway.
Cell Immunol
137:429, 1991[Medline]
[Order article via Infotrieve]
16.
Bulens C, Willems F, Delvaux A, Pièrard G, Delville JP, Velu T, Goldman M:
Interleukin-10 differentially regulates B7-1 (CD80) and B7-2 (CD86) expression on human peripheral blood dendritic cells.
Eur J Immunol
25:2451, 1995
17.
Turka LA, Ledbetter JA, Lee K, June CH, Thompson CB:
CD28 is an inducible T cell surface antigen that transduces a proliferative signals in CD3+ mature thymocytes.
J Immunol
144:1646, 1990[Abstract]
18.
Linsley PS, Greene JL, Tan P, Bradshaw J, Ledbetter JA, Anasetti C, Damle NK:
Coexpression and functional cooperation of CTLA-4 and CD28 on activated T lymphocytes.
J Exp Med
176:1595, 1992[Abstract/Free Full Text]
19.
Thompson CB, Lindsten T, Ledbetter JA:
CD28 activation pathway regulates the production of multiple T-cell derived lymphokines/cytokines.
Proc Natl Acad Sci USA
91:3260, 1994[Abstract/Free Full Text]
20.
Kanai T, Thomas EK, Yasumoti Y, Letvin K:
IL-15 stimulates the expansion of AIDS virus-specific CTL.
J Immunol
157:2681, 1996
21.
Julien D, Sieling PA, Uyemara K, Mar ND, Rea TH, Modlin RL:
IL-15, an immunomodulator of T cell responses in intracellular infection.
J Immunol
158:800, 1997[Abstract]
22.
Nishimura H, Hiromats K, Kobayashi N, Grabstein KH, Paxton R, Sugamura K, Bluestono JA, Yoshikai Y:
IL-15 is a novel growth factor for murine gamma delta cells induced by Salmonella infection.
J Immunol
156:663, 1996[Abstract]
23.
Kahn IA, Kasper LH:
IL-15 augments CD8+ T cell mediated against Toxoplasma gondii infection in mice.
J Immunol
157:2103, 1996[Abstract]
24.
Kacabi L, Stoiber H, Dierich MP:
Role of IL-15 in HIV-associated hypergammaglobulinemia.
Clin Exp Immunol
108:14, 1997[Medline]
[Order article via Infotrieve]
25.
Jonuleit H, Wiermann K, Muller G, Degwert J, Hoppe U, Knop J, Enk AH:
Induction of IL-15 messenger RNA and protein in human blood-derived dendritic cells. A role for IL-15 in attraction of T cells.
J Immunol
158:2610, 1997[Abstract]
26.
Doherty TM, Seder RA, Sher A:
Induction and regulation of IL-15 expression in murine macrophages.
J Immunol
156:735, 1996[Abstract]
27.
Bouscart F, Levacher M, Landman R, Muffat-Joly M, Girard PM, Saimon AG, Brun-Vezinet F, Sinet M:
Changes in blood CD8+ lymphocytic activation status and plasma HIV RNA levels during antiretroviral therapy.
AIDS
12:1267, 1998[Medline]
[Order article via Infotrieve]
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati What's this?
This article has been cited by other articles:
|
|
|
|
 
B G G Oliver, S Lim, P Wark, V Laza-Stanca, N King, J L Black, J K Burgess, M Roth, and S L Johnston
Rhinovirus exposure impairs immune responses to bacterial products in human alveolar macrophages
Thorax,
June 1, 2008;
63(6):
519 - 525.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. M. Bhorade, A. Yu, W. T. Vigneswaran, C. G. Alex, and E. R. Garrity
Elevation of Interleukin-15 Protein Expression in Bronchoalveolar Fluid in Acute Lung Allograft Rejection
Chest,
February 1, 2007;
131(2):
533 - 538.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. He, S. Reichow, S. Ramamoorthy, X. Ding, R. Lathigra, J. C. Craig, B. W. S. Sobral, G. G. Schurig, N. Sriranganathan, and S. M. Boyle
Brucella melitensis Triggers Time-Dependent Modulation of Apoptosis and Down-Regulation of Mitochondrion-Associated Gene Expression in Mouse Macrophages
Infect. Immun.,
September 1, 2006;
74(9):
5035 - 5046.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. M. Beck
The Immunocompromised Host: HIV Infection
Proceedings of the ATS,
December 1, 2005;
2(5):
423 - 427.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
R. D. Mason, M. I. Bowmer, C. M. Howley, and M. D. Grant
Cross-Reactive Cytotoxic T Lymphocytes against Human Immunodeficiency Virus Type 1 Protease and Gamma Interferon-Inducible Protein 30
J. Virol.,
May 1, 2005;
79(9):
5529 - 5536.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. M. BECK, M. J. ROSEN, and H. H. PEAVY
Pulmonary Complications of HIV Infection . Report of the Fourth NHLBI Workshop
Am. J. Respir. Crit. Care Med.,
December 1, 2001;
164(11):
2120 - 2126.
[Full Text]
[PDF]
|
|
|
|
|
|
|
F. Mattei, G. Schiavoni, F. Belardelli, and D. F. Tough
IL-15 Is Expressed by Dendritic Cells in Response to Type I IFN, Double-Stranded RNA, or Lipopolysaccharide and Promotes Dendritic Cell Activation
J. Immunol.,
August 1, 2001;
167(3):
1179 - 1187.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. AGOSTINI, M. SIVIERO, M. FACCO, D. CAROLLO, G. BINOTTO, A. TOSONI, A. M. CATTELAN, R. ZAMBELLO, L. TRENTIN, and G. SEMENZATO
Antiapoptotic Effects of IL-15 on Pulmonary Tc1 Cells of Patients with Human Immunodeficiency Virus Infection
Am. J. Respir. Crit. Care Med.,
February 1, 2001;
163(2):
484 - 489.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
T. A. Fehniger and M. A. Caligiuri
Interleukin 15: biology and relevance to human disease
Blood,
January 1, 2001;
97(1):
14 - 32.
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. AGOSTINI, M. FACCO, M. SIVIERO, D. CAROLLO, S. GALVAN, A. M. CATTELAN, R. ZAMBELLO, L. TRENTIN, and G. SEMENZATO
CXC Chemokines IP-10 and Mig Expression and Direct Migration of Pulmonary CD8+/CXCR3+ T Cells in the Lungs of Patients with HIV Infection and T-Cell Alveolitis
Am. J. Respir. Crit. Care Med.,
October 1, 2000;
162(4):
1466 - 1473.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. M. Mastroianni, G. d'Ettorre, G. Forcina, M. Lichtner, F. Mengoni, C. D'Agostino, A. Corpolongo, A. P. Massetti, and V. Vullo
Interleukin-15 enhances neutrophil functional activity in patients with human immunodeficiency virus infection
Blood,
September 1, 2000;
96(5):
1979 - 1984.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
I. A. Khan and L. Casciotti
IL-15 Prolongs the Duration of CD8+ T Cell-Mediated Immunity in Mice Infected with a Vaccine Strain of Toxoplasma gondii
J. Immunol.,
October 15, 1999;
163(8):
4503 - 4509.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
Top
Abstract
Introduction