SIGNALS THROUGH T-CELL RECEPTOR-XI CHAIN ALONE ARE INSUFFICIENT TO PRIME RESTING T-LYMPHOCYTES

Activation studies performed with transfected T cell hybridomas and tu mors revealed that chimeric molecules containing the CD3 epsilon or ze ta chain intracytoplasmic portions can induce the complete effector fu nctions normally seen only when the complete T cell receptor (TCR)/CD3 complexes of T lymphocytes are triggered. Therefore, the zeta chain, with its three antigen recognition activation motives, is thought to c onnect the antigen-binding Ti chains with the intracellular signaling machinery of the T cell. Here we demonstrate that the cytoplasmic port ion of the TCR-zeta chain is not sufficient to activate resting T lymp hocytes when cells from transgenic mice expressing a chimeric zeta rec eptor are used. However, after (in vivo and in vitro) activation throu gh their endogenous TCR/CD3 complexes, the preactivated T lymphocytes could be triggered through the zeta chimera to the same extent as when they were activated through their endogenous TCR/CD3 complexes. They were able to proliferate and elicit cytotoxic functions when triggered through their zeta chimeras. These results suggest that the triggerin g requirements for effector functions seem to be different in resting than in activated T cells.