Blood, Vol. 95 No. 11 (June 1), 2000:
pp. 3628-3630
BRIEF REPORT
Expression of CD94/NKG2A and killer immunoglobulin-like receptors
in NK cells and a subset of extranodal cytotoxic T-cell lymphomas
Wolfgang Haedicke,
Faith C. S. Ho,
Andreas Chott,
Lorenzo Moretta,
Thomas Rüdiger,
German Ott, and
Hans Konrad Müller-Hermelink
From the Institute of Pathology, University of Würzburg,
Würzburg, Germany; the Department of Pathology and
Immunology, Monash University, Melbourne, Australia; the
Institute of Clinical Pathology, University of Vienna,
Austria; the Dipartimento di Medicina Sperimentale, University of
Genoa, and Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy.
 |
Abstract |
Thirty-two natural killer (NK) and cytotoxic T-cell lymphomas and 14 noncytotoxic nodal T-cell lymphoma controls were immunostained with the
use of monoclonal antibodies reactive against NK-cell receptor (NKR)
molecules (CD94, NKG2A, p58.2, p58.1, p140, p70, p50.3). All NK-cell
lymphomas (4 nasal/oral and 1 intestinal) expressed at least 1 NKR, the
CD94/NKG2A complex. Two were positive for 1 or more killer
immunoglobulin-like receptors. Of 15 extranodal cytotoxic T-cell
lymphomas, 3 expressed CD94, including 2 intestinal and 1 hepatosplenic
T-cell lymphomas. In contrast, none of the nodal lymphomas were
positive. Detection of NKRs may provide a useful tool to confirm the
diagnosis of NK-cell lymphomas and to delineate a subgroup of cytotoxic
T-cell lymphomas. Expression of NKRs only in extranodal cytotoxic
T-cell lymphomas might reflect differences in the homing capabilities
of cytotoxic T cells expressing NKRs in normal individuals and might be
influenced in part by localized chronic immune reactions.
(Blood. 2000;95:3628-3630)
© 2000 by The American Society of Hematology.
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Introduction |
Interest in the natural killer (NK) cell has gathered
momentum in the last decade, in particular, because many of the
molecular mechanisms underlying its function have now been
elucidated.1-3 Lymphomas arising from NK cells and the
related extranodal T-cell lymphomas of cytotoxic phenotype (ETLCP) have
also been recognized.4-9 These are a heterogeneous group of
neoplasms, having in common the expression of 1 or more of the
cytotoxic granule associated proteins, but the major types have been
more clearly defined by hematopathologists in recent
years.10,11 However, identification of NK-cell lymphomas
and their distinction from ETLCP can still be problematic, depending on
negative features, such as the lack of T-cell receptor (TCR) peptide
expression, absence of CD3 on the cell membrane, and a germline
configuration of the TCR genes. CD56 is a useful, but not
specific, marker for NK cells, and its role in the function of the NK
cell is as yet unknown.12
The discovery of major histocompatibility complex (MHC) class
I-specific NK cell receptors (NKRs), of either the inhibitory or the
activatory type, has provided much insight into the control of NK-cell
function.13,14 Engagement of inhibitory NKRs by normal
self-MHC class I alleles on potential target cells leads to inhibition
of cytotoxicity, whereas loss of such normal alleles in virus-infected,
transformed, or allogeneic cells leads to loss of inhibition and allows
stimuli that activate NK cytotoxicity to come into play. Similar
receptors have been detected on a small subset of cytotoxic
T-lymphocytes, both in the peripheral blood and in lymphoid
tissues,15 and there is evidence that these NKR+ T cells are oligoclonal populations of memory T cells
generated as a consequence of chronic antigenic
stimulation.16 Identification of NKRs on lymphomas of NK
and T-cell lineage may therefore be used to confirm the cell type and
has the potential to delineate a special biological group of tumors.
To our knowledge, there is no published study on the occurrence of NKRs
on NK and T-cell lymphomas. The purpose of this brief report is to
present the preliminary results of such a study.
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Materials and methods |
Case selection
A total of 46 lymphoid malignancies of T- and NK-cell origin were
retrieved from the files of the Lymph Node Reference Center and the
surgical pathology files of the Institute of Pathology at the
University of Würzburg, Germany, and of the Institute of Clinical
Pathology at the University of Vienna, Austria. Twenty of these were
extranodal lymphomas (Table 1) and 12 were
nodal lymphomas (8 peripheral T-cell lymphomas not otherwise specified and 4 anaplastic large-cell lymphomas). They were chosen to represent the major categories of cytotoxic lymphoid neoplasms, expressing at
least 1 of the 2 cytotoxic granule-associated proteins,
TIA1 or granzyme B. Five angioimmunoblastic T-cell
lymphomas (AILs), 9 periperal T-cell lymphomas of
noncytotoxic origin, and 13 specimens from various normal and reactive
lymphoid tissues (5 lymph nodes, 5 spleens, and 3 tonsils) were
included as controls.
Immunohistochemistry
Monoclonal antibodies against 7 NKRs (
CD94/XA185; NKG2A/Z270;
EB6/p58.1; p58.2/GL183; p140/Q66; p70/Z27; and
p50.3/FST172) were produced in the laboratory of L.M. Other primary
antibodies were purchased from the following sources: CD3 (paraffin
sections, DAKO, Copenhagen, Denmark; frozen sections, Becton Dickinson, Mountain View, CA); CD5 (DAKO); CD56 (1:20) (Novocastra, Newcastle, Great Britain); TIA1 (1:800) (Coulter Immunology, Hialeah, FL); granzyme B (1:20) (Monosan, Uden, The Netherlands), 
F1 (1:10) and TCR (1:10) (T-cell Diagnostics, Woburn, MA).
For NKR staining, acetone fixed cryostat sections were air dried and
incubated with the primary antibody for 30 minutes (0.5% phosphate-buffered saline [PBS]) at room temperature, followed by
horseradish peroxidase (HRP)-labeled rabbit antimouse antibody (1:50
in 30% human plasma with 70% PBS) for 30 minutes and subsequently with an HRP-labeled goat antirabbit antibody for 30 minutes at room
temperature. Color was routinely developed with the use of diamino-benzidine (DAB). Paraffin sections were stained
as described recently.17
Stains were scored as positive if more than 50% of the malignant
(morphologically atypical) cells were positive.
Clonal TCR gene rearrangement was determined by means of a
polymerase chain reaction assay amplifying the TCR chain gene as
previously described.18
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Results and discussion |
Results of immunostaining for the NKRs in extranodal lymphomas are
shown in Table 1 and Figure 1.
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| Fig 1.
Results of immunostaining for the NKRs in extranodal
lymphomas.
(A) (B) Nasal NK cell lymphoma (case 2): nasal biopsy. Most pleomorphic
small-to- medium-sized cells are (A) CD94+ and (B) p140+.
(C) Hepatosplenic / T-cell lymphoma (case 5): splenectomy
specimen. Most of the medium-sized and large transformed cells are
p58.2+. (D) Preserved intestinal mucosa adjacent to a lymphomatous
infiltrate. Scattered lamina propria lymphocytes are p50.3+.
|
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It is significant that all 5 NK lymphomas (Figure 1A and 1B), without
exception, expressed CD94/NKG2A. These 2 molecules assemble to a
heterodimer and belong to the family of lectin-type NKR. Its specific
ligand has been shown to be HLA-E.18,19 NKRs of the lectin
superfamily are expressed in the majority of NK cells.19 This provides a clue as to how the indiscriminate killing of bystander cells by NK tumors may be kept in check.
In contrast, the total repertoire of NKRs of the immunoglobulin
superfamily, so-called killer immunoglobulin-like receptors (KIRs), of
both the inhibitory and the activatory type expressed by all the NK
cells in an individual is variable, and each receptor is expressed only
on a subset of the individual's NK cells.20 Most human
NK-cell clones have been found to simultaneously express 2 or more NKRs
of the KIR and CD94/NKG2 families combined.21 Expression of
1 or 2 KIRs was found in only 2 of the 5 NK lymphomas studied. The only
activatory receptor tested (p50.3) was not detected in any of the
lymphomas. The significance of this relatively low level of detection
of NKRs of the immunoglobulin superfamily is not known at present
Of the nodal and extranodal cytotoxic T-cell lymphomas, only 3 expressed CD94. This is consistent with the fact that only a small
subset of cytotoxic T cells are NKR-positive.15 All 3 positive cases were extranodal lymphomas. Of these, only the hepatosplenic T-cell lymphoma (HSTCL, Figure 1C) additionally expressed 2 KIRs (p58.2, p58.1). Two or more NKRs have been detected on
a single T-cell.15,16 The other 2 positive cases were
intestinal T-cell lymphomas, of which 1 was confirmed to be of
T-cell lineage, on the basis of the expression of F1 but not
of TCR. Both were CD56
. Three of the
intestinal lymphoma samples contained preserved intestinal mucosa
adjacent to the NKR-negative lymphomatous infiltrate. In these areas,
scattered small lymphoid cells of the lamina propria stained for all
NKRs tested, whereas no reactivity was observed on intraepithelially
distributed cells. (Figure 1D). Studies are underway to investigate the
NKRs' status on human mucosal lymphocytes in normal and inflamed
intestine as these cells differ significantly from peripheral
blood lymphocytes with respect to phenotypical and functional
properties.22-24
Of the NKR-negative cases, 4 were CD56+ T-cell lymphomas
(cases 6, 10, 11, and 20). It is evident that CD56 positivity need not
be associated with NKR positivity. None of the nodal T-cell lymphomas
of cytotoxic or noncytotoxic phenotype expressed any of the NKRs,
although occasional NKR-positive cells were found scattered among the
tumor cells. In the reactive lymphoid tissues, scattered NKR-positive
cells were also found. In the normal spleen, CD94 positivity was found
in up to 20% of all lymphoid cells, whereas KIR-positive cells were
less numerous, accounting for less than 5% of all lymphoid cells.
T cells share many similarities with NK cells, including
expression of KIRs at higher levels than T cells.25
It is therefore interesting to note that the HSTCL was the only T-cell
lymphoma studied that expressed the KIRs. Moreover, in this case, more
than 70% of all the tumor cells showed staining with 4 of the NKR
antibodies, whereas none stained with the other 3 antibodies. The
uniform expression of several KIRs on the vast majority of cells
appears to be a definite hint for a clonal proliferation rather than a
reactive process, although this is by no means as specific as TCR gene
rearrangement studies for determining clonality, and reactive T-cell
proliferations have also been shown to be monoclonal or oligoclonal in
type.16 However, in the context of NK-cell lymphomas, the
feasibility of using NKR staining patterns for identifying clonal
populations of NK cells should be further explored as there is
presently no tool available for assessing monoclonality in NK cell lymphomas.
Further studies are also required to determine whether the expression
of NKRs delineates a biologically distinct group of T-cell lymphomas
and to relate this to their pathogenesis, including possible
association with sites of chronic antigenic stimulation.
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Footnotes |
Submitted August 11, 1999; accepted January 26, 2000.
Supported by the Sonderforschungsbereich 172 of the
University of Würzburg; supported in part by Associazione
Italiana per la Ricerca sul Cancro (AIRC) and Ministero dell'
Università e della Ricerca Scientifica e Tecnologica
(MURST).This study was done in part while F.C.S.H. was a guest
professor at the University of Würzburg.
Reprints: Hans Konrad Müller-Hermelink,
Pathologisches Institut, Universität Würzburg, Josef
Schneider Str 2, D 97080 Würzburg, Germany; e-mail:
path062{at}mail.uni-wuerzburg.de.
The publication costs of this
article were defrayed in part by
page charge payment. Therefore,
and solely to indicate this fact,
this article is hereby marked
"advertisement"
in accordance with 18 U.S.C.
section 1734.
| |
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Abstract
Introduction
