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.

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.