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The mechanism through which CD28 costimulation potentiates TCR-driven gene expression is still not clearly defined. Vav-1, an exchange factor for Rho GTPases thought to regulate, mainly through Rac-1, various signaling components leading to cytokine gene expression, is tyrosine phosphorylated upon CD28 engagement. Here, we provide evidence for a key role of(More)
We have previously shown that a tyrosine to leucine replacement in the transmembrane region of T cell receptor (TCR)-beta results in a deficient induction of CD95-L and apoptosis upon TCR triggering in a transfected T cell line. By contrast, interleukin (IL)-2 production and the expression of CD25 and CD69 were normally induced. Since the mutation in(More)
Engagement of the TCR by ligand results in its intern a-lization and downregulation by at least two mechanisms. One is predominant at low concentrations of ligand, re q u i re s signaling and downregulates non-triggered receptors. The second re q u i res direct engagement and is independent of sig-naling. We now describe that when engaged with high doses of(More)
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