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CORRESPONDENCE We read with great interest the report of Delfau-Larue et
al1 on the ongoing discussion about the significance of
dominant T-cell clones as a hallmark of T-cell malignancy. The authors showed the occurrence of dominant T-cell clones in the peripheral blood
of patients with cutaneous T-cell lymphoma (CTCL) (30%), non-CTCL-related skin diseases (41%), and other benign infiltrates (34%). From these findings, they conclude that demonstration of T-cell
clonality in the peripheral blood is not of undetermined significance,
but of no significance at all. Based on our own results, we
wish to point out the view shared by many investigators using
polymerase chain reaction (PCR) for clonality studies: that, with some technical precautions taken, T-cell receptor gene
rearrangement analysis is reliable and specific and may considerably
add to the diagnosis of malignant lymphoproliferative disorders,
even in peripheral blood. We are well aware that expansion of T-cell clones is a
prerequisite for antigen-specific T-cell responses and that
T-cell clones may be present under many reactive conditions. Therefore, it is not surprising that different PCR-based methods are able to
amplify dominant T-cell clones with varying frequency depending on
their sensitivity. We have shown that overinterpretation of these
dominant PCR products with respect to the diagnosis of malignancy can
be avoided by repeated independent PCR determinations of the same
samples and application of high resolution separation techniques such
as GeneScan analysis and/or sequencing.2 Under reactive conditions dominant PCR products vary, whereas under malignant conditions dominant PCR products are exactly reproducible. Our investigation of 21 clear-cut benign skin infiltrates (psoriasis and
contact dermatitis) revealed dominant T-cell clones in only 3 cases.
Repeated PCR and GeneScan analyses of these 3 samples demonstrated that
the dominant amplificates were of different size, indicating the
presence of several different predominant T-cell clones in these
lesions. Therefore, we decided to consider cases that do not
show identical dominant PCR products in repeated PCR analyses of the
same sample as pseudo monoclonal. Here, we show that this holds also true for peripheral blood
samples of patients with cutaneous T-cell lymphoma (CTCL),
parapsoriasis, and pseudo T-cell lymphoma (Table
1). Similar to the results of
Delfau-Larue et al, 19 of 30 cases (63%) of parapsoriasis and pseudo
T-cell lymphoma showed a dominant T-cell clone in the peripheral blood at prima vista analysis. But repeated analysis of these samples
revealed PCR products of different size, that is, pseudo monoclonality,
in all but 1 of the samples, so that the truely monoclonal cases in
these nonmalignant conditions amounted to just 3.3%. In stage IV CTCL
patients, the opposite picture appeared: the prima vista dominant PCR
products seen in 9 of 11 patients (81.8%) were confirmed by repeated
analysis of the same sample. In addition, identical amplificates were
generated from lesional skin and peripheral blood samples in these 9 patients, further confirming T-cell clonality in different lymphocyte
recirculation compartments as expected from T-cell malignancies. In
contrast, true T-cell clonality is a very rare finding under
nonmalignant conditions; in such cases, the term "T-cell clonality of
undetermined significance" should be reserved, in analogy to
the term "monoclonal gammopathy of undetermined significance." In
the study by Delfau-Larue et al, only 6% of 211 patients with non-CTCL
lesions showed the same clonal T-cell population (of undetermined
significance) after denaturing gradient gel electrophoresis (DGGE)
analysis in skin and peripheral blood; the identity of the comigrating
bands, however, should be confirmed by an independent assay with higher
resolution such as GeneScan analysis or sequencing.3
Patients with clinically clear-cut nonmalignant conditions and
confirmed T-cell clonality should be carefully documented and followed
to further determine the natural course of T-cell clonality of
undetermined significance.
In summary, we wish to suggest that "dominant T-cell clone"1 is a rather technical term of still unknown clinical relevance which should be interpreted carefully. The term "clonality"1 should only be used when pseudo monoclonality has been excluded by repeated independent PCR determinations. Under these considerations, the analysis of peripheral blood samples of patients suffering from cutaneous T-cell lymphoproliferative diseases is of high diagnostic value.
Edgar Dippel, Detlev Klemke, Michael Hummel, Harald Stein, and Sergij Goerdt
References
1.
Delfau-Larue M-H, Laroche L, Wechsler J, et al.
Diagnostic value of dominant T-cell clones in peripheral blood in 363 patients presenting consecutively with a clinical suspicion of cutaneous lymphoma.
Blood.
2000;96:2987-2992 2. Dippel E, Assaf C, Hummel M, et al. Clonal T-cell receptor gamma-chain gene rearrangement by PCR-based GeneScan analysis in advanced cutaneous T-cell lymphoma: a critical evaluation. J Pathol. 1999;188:146-154[CrossRef][Medline] [Order article via Infotrieve].
3.
Assaf C, Hummel M, Dippel E, et al.
High detection rate of T-cell receptor beta chain rearrangements in T-cell lymphoproliferations by family specific polymerase chain reaction in combination with the GeneScan technique and DNA sequencing.
Blood.
2000;96:640-646
Response:Peripheral blood T-cell clonality of no cutaneous T-cell lymphoma diagnostic valueI thank Dr Dippel and his colleagues for their comments on our report concerning the diagnostic value of peripheral blood (PB) T-cell clonality in clinical suspicion of CTCL. We have argued that demonstration of T-cell clonality in PB is of unknown significance (not "of no significance") and, more precisely, that it has no CTCL diagnostic value as long as the same clone has not been identified in the skin (in contrast to Gene Scan analysis, DGGE migration of PCR products depends on CDR3 sequences and not only on CDR3 size). By contrast, identification of the same clone in skin and blood is of high diagnostic value. As Dippel et al remind us, PB T-cell clonal expansions occur in
multiple clinical settings.1 For example, peripheral blood expansion of CD8+ clones have been described in healthy
individuals, as well as in patients with rheumatoid arthritis, and have
been shown to be remarkably stable over time (up to 4 years).2 They increased with age in both the
CD45RA+ (naive or long-life memory cells) and
CD45RO+ (memory) compartments.3 Accordingly,
it has been our experience that, using PCR Finally, although Dippel et al's concept of "pseudoclonality" seems to us of no physiologic relevance, we agree with them that the study of peripheral blood samples in patients with a suspicion of CTCL is helpful for the diagnosis as long as the same T-cell clone is detectable in both skin and blood samples.
Marie-Hélène Delfau-Larue
References 1. Maini MK, Casorati G, Dellabona P, Wack A, Beverley PC. T-cell clonality in immune responses. lmmunol Today. 1999;20:262-266[CrossRef][Medline] [Order article via Infotrieve]. 2. Fitzgerald JE, Ricalton NS, Meyer AC, et al. Analysis of clonal CD8+ T cell expansions in normal individuals and patients with rheumatoid arthritis. J Immunol. 1995;154:3538-3547[Abstract].
3.
Wack A, Cossarizza A, Heltai S, et al.
Age-related modifications of the human alphabeta T cell repertoire due to different clonal expansions in the CD4+ and CD8+ subsets.
Int Immunol.
1998;10:1281-1288
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| Copyright © 2001 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
-DGGE, we detect a T-cell
clone, dominant over polyclonal background, in the blood of 30% to
40% of studied patients, whether with cutaneous malignancy or benign
disease. Moreover, dominant T-cell clones are increasingly
detected with age, and once detected in a given patient, the T-cell
clone remained detectable on all 2001 serial samples with a follow-up
as long as 6 years (unpublished data, 2001).
