Definition of discrete signals involved in human T-cell activation.

Mitogenic activities of monoclonal antibodies directed at defined receptor structures expressed on the surface of mature human T lymphocytes were employed to study, in detail, signals involved in primary T-cell activation. Based on differential requirements for stimulation, two discrete pathways of human T-cell activation can be defined: the antigen-induced mode of activation initiated through the Ti-T3 antigen-receptor complex and an alternative pathway which can be triggered by monoclonal antibodies directed at the T11 glycoprotein. Perhaps more importantly, the approach taken here allows the definition of stable intermediate cellular stages within the activation cascade and, thus, to analyze the signalling capabilities of individual receptor molecules.