T cell activation: differences in the signals required for XXXX production by nonactivated and activated T cells.

@entity1199 @entity3647 @entity1192 @entity3457
Soluble antibodies against the T3/antigen receptor complex alone are not sufficient to induce proliferation and @entity1199 expression by T lymphocytes. An additional requirement is the presence of accessory cells (AC). In this model, AC provide at least two functions required for T cell activation: 1) the surface interaction of T3 antibodies with Fc receptors on the AC surface and 2) the production of soluble mediators such as @entity1192 ( @entity1192 ). In the experiments reported here, these stimuli are represented by T3 antibodies immobilized onto Sepharose beads and by recombinant @entity1192 . In this study we investigated differences in activation requirements in resting and activated T cells. Resting T cells were represented by AC-depleted peripheral blood mononuclear cells (PBMC) or the T cell line Jurkat, which phenotypically resembles a resting T cell. @entity3457 cells were represented by T cell clones and the T cell line HUT 78, which express the activation molecules Ia and the @entity3647 (Tac). In resting cells, activation required the presence of three different signals: perturbation of the T3/antigen receptor complex by T3 antibodies, surface redistribution of T3/antigen receptor complexes, and presence of @entity1192 . In contrast, activated T cells require only perturbation and redistribution of T3/antigen receptor complexes and not @entity1192 for the induction of proliferation or @entity1199 production. Possible mechanisms of intracellular signaling for these stimuli are discussed.
