Idiotype-specific autologous T-cell interactions restricted by HLA-DR

T lymphocytes, primed in vitro to alloantigens were shown to acquire a profound capacity to stimulate autologous T-cell proliferative responses. Both PBLs and purified peripheral T cells responded to alloreactive aTLCs, suggesting that the T/T interaction did not require processing and presentation of antigen by APCs. The T/T interactions were intrinsically MHC restricted, since the autologous T-cell response was blocked by the addition of mAbs to HLA-DR. In secondary responses, primed T-cell lines responded with a higher magnitude to the priming aTLC relative to other aTLCs with different alloantigenic specificities. This specificity of response supports a model of idiotypic TcR recognition by the responding cells. Indeed, TcR protein purified from the cell surface of the priming aTLC could stimulate the primed T-cell lines in secondary responses. Reciprocal interactions between TcRs were ruled out. These data suggest that T-cell-mediated, MHC-restricted, TcR-specific, autologous T-cell responses may be important in peripheral immune regulation.