T lymphocytes, primed in vitro to alloantigens were shown to acquire a
profound capacity to stimulate autologous T-cell proliferative respon
ses. Both PBLs and purified peripheral T cells responded to alloreacti
ve aTLCs, suggesting that the T/T interaction did not require processi
ng and presentation of antigen by APCs. The T/T interactions were intr
insically MHC restricted, since the autologous T-cell response was blo
cked by the addition of mAbs to HLA-DR. In secondary responses, primed
T-cell lines responded with a higher magnitude to the priming aTLC re
lative 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 s
urface of the priming aTLC could stimulate the primed T-cell lines in
secondary responses. Reciprocal interactions between TcRs were ruled o
ut. These data suggest that T-cell-mediated, MHC-restricted, TcR-speci
fic, autologous T-cell responses may be important in peripheral immune
regulation.