FIG. 1.

Inhibition of the PI 3-kinase lipid kinase activity completely abrogates the CD5-induced upregulation of the IL-2 promoter activity in activated human T lymphocytes. (A and B) Human T lymphocytes were left unstimulated or stimulated with PHA plus anti-CD28 (αCD28) ± anti-CD5 (αCD5) in the presence or absence of 100 nM wortmannin (A) or 1 μM LY294002 (B), both inhibitors of PI 3-kinase. Cell-free supernatants were harvested after 24 h and analyzed for secreted IL-2 protein. The mean values ± SEMs for the IL-2 secretion observed in four independent experiments are shown. (C) Human T cells, prestimulated as described in Materials and Methods, were transfected with 15 μg of pCAT3e-IL-2(−319/+47) together with 15 μg of either an empty control expression plasmid (control) or the expression plasmid for a dominant negative p85 mutant (Δp85). Transfected cells were left alone for 1 h, divided into three groups, and subsequently left unstimulated or stimulated with PHA plus anti-CD28 (αCD28) or PHA plus anti-CD28 and anti-CD5 (αCD5) for 24 h. CAT expression was measured as described in Materials and Methods. The results are expressed as the relative CAT expression compared to the PHA- plus anti-CD28-induced CAT expression in the transfected control T cells, which was set at 1. The mean values ± SEMs found for the relative CAT expression in three independent experiments are shown.