C-type lectin-like receptors in peptide-specific HLA class I-restricted cytotoxic T lymphocytes: differential expression and modulation of effector functions in clones sharing identical TCR structure and epitope specificity

Abstract

C-type lectin-like inhibitory receptors are heterodimers consisting of CD94 and NKG2-A-B molecules expressed on NK cells and on a subset of activated T lymphocytes. Their inhibitory effects on NK cytotoxicity and on the NK-like activity of T cell clones have been demonstrated, but no data are currently available on antigen-specific class I-restricted cytotoxic T lymphocytes (CTL). We have generated a panel of HLA-A2.1-restricted CTL clones directed against a nonapeptide derived from a melanoma-associated antigen, dopachrome tautomerase (TRP-2). All clones were CD8+ and TCR alphabeta+. About half of them expressed a CD94bright phenotype, whereas the remaining were CD94dim. Only the CD94bright CTL expressed the NKG2-A-B gene, consistent with the expression of a C-type, lectin-like, inhibitory CD94/NKG2-A-B heterodimer. Both CD94bright and CD94dim clones appeared to require similar amounts of synthetic epitope sensitizing target cells. Addition of anti-CD94 mAb resulted in a significant increase of specific killing by CD94bright, but not by CD94dim clones in the presence of suboptimal concentrations of peptide, whereas, when optimal amounts were used, the mAb did not induce a significant modulation of the cytotoxicity. Antigen-induced inward [Ca2+]i fluxes were unaffected, but an enhancement of TCR down-modulation could be observed in the presence of anti-CD94 mAb at high concentration of antigenic peptide. The analysis of the TCR-Vbeta repertoire of the CTL clones by RT-PCR and immunofluorescence revealed that all clones regardless of CD94 phenotype shared Vbeta22 expression. Most importantly, sequence analysis showed that they all expressed identical Vbeta22 TCR rearranged with Jbeta2.1 and Cbeta2. Taken together, these data indicate that different expression of functionally active lectin-like inhibitory receptors can be detected in CTL clones sharing identical TCR sequence and peptide specificity.

Expression of MHC class I receptors confers functional intraclonal heterogeneity to a reactive expansion of γδ T cells

“…This concerned both the lectin-and Ig-like MHC-NKR, even though the first was quantitatively more expressed than the second, as previously observed for polyclonal peripheral blood cd T lymphocytes [24]. This observation lends further support to the conclusions deduced from the results previously obtained on clones generated in vitro [9][10][11], because it has the advantage to be done on freshly isolated PBMC. Accordingly, we noted here that the Ig-and lectin-like MHC-NKR phenotype of in vitro derived T cell clones did not strictly correspond to that of the fresh PBMC.…”

“…This was also the case for CD94 + NKG2A + Vd4/Vc5 T cell clones whose cytotoxic potential was not affected by mAb HP3B1, although membrane expression of the heterodimer was proven by flow cytometry. Similar negative results have previously been reported for CD8 ab T cell clones [10,26]. We thus cannot conclude on the functional role of these different heterodimers in the cytotoxic function of these clones and cannot exclude that the presence of NKG2 transcripts in CD94 low cells does not necessarily result in heterodimer membrane expression.…”

“…Some reports suggested that in vivo MHC-NKR expression might follow the law of "all or none", at least in T cell leukemias [7,8], whereas others revealed that several anti-EBV [9], anti-tumoral [10] or donor peripheral blood [11] CD8 + ab T cell clones can display different patterns of Ig-like or lectin-like MHC-NKR even when they express identical TCR. Taken altogether, these results sustain the notion that MHC-NKR expression occurs after TCR rearrangement.…”

Activating CD94:NKG2C and inhibitory CD94:NKG2A receptors are expressed by distinct subsets of committed CD8+ TCR αβ lymphocytes

“…CD94:NKG2A is present on effector cells as well as on memory cells that recirculate in lymph nodes. However, in humans NKG2A appears not to be expressed by virus-specific lymphocytes [18][19][20] but rather by cells recognizing tissue differentiation antigens [6,[14][15][16][17]. One could argue that if the autoreactivity of these cells is controlled by the expression of the inhibitory CD94:NKG2A receptor [33], dendritic cells expressing costimulatory molecules induced by pathogen-derived products could break this tolerance.…”

“…In humans, the situation may be quite different. The only CD94 + T cells with a known antigen specificity described to date recognize tumor-associated tissue differentiation antigens [6,[14][15][16][17], whereas CD8 + T cells specific for herpes B [18], CMV [19], or for EBV during acute mononucleosis [18,20] do not express CD94. Interestingly, many intraepithelial T lymphocytes express CD94:NKG2A [9], suggesting that its expression is induced after recognition of particular antigens and/or under particular conditions of antigenic stimulation.…”