Transmembrane signalling via the T cell antigen receptor heterodimer and the CD2 antigen. A synergistic pathway for activation of T cells.

T cell surface proteins involved in transmembrane signalling resulting in the activation of T cells were investigated utilizing as probes monoclonal antibodies directed at T cell surface antigens. Here we report that mAbs that react with a framework determinant of alpha/beta heterodimer of T cell receptor for antigen, anti-TCR-1, and those with the SRBC-binding epitope of the CD2 antigen, OKT11, are synergistic in promoting T cell proliferation. The proliferative response is dependent upon crosslinking of anti-TCR-1 and OKT11, and is associated with a significant increase in the concentration of intracellular free calcium in T cells. Moreover, EGTA and a direct (staurosporine) or a competitive (1-[5-isoquinolinylsulfonyl]-2-methyl piperazine) inhibitor of protein kinase C prevents T cell proliferation accomplished with crosslinked anti-TCR-1 and OKT11. Our findings, in addition to demonstrating the synergism between the signals initiated via the T cell receptor for antigen and the CD2 antigen, suggest a role for calcium and protein kinase C in the transduction of signals generated with crosslinked anti-TCR-1 and OKT11.