Phosphatidylinositol 3‐kinase inhibitors prevent mouse cytotoxic T‐cell development in vitro

To become competent killer cells, CD8 + T cells requirestimulation through signal transduction pathways associated with the T‐cell receptor, costimulatory molecules such as CD28, and cytokinereceptors such as the interleukin (IL)‐2 receptor. We used wortmanninand LY294002, two inhibitors of phosphatidylinositol 3‐kinase (PI3‐K), to study the role of PI3‐K in mouse cytotoxic T‐lymphocyte (CTL)induction in response to mitogenic anti‐CD3 antibody. Anti‐CD3‐inducedCD8 + T‐cell proliferation and CTL development wereinhibited dose dependently by both PI3‐K inhibitors. IL‐2 synthesis byanti‐CD3‐activated CD8 + T cells was also diminished byPI3‐K inhibition. PI3‐K inhibition resulted in a modest decrease inanti‐CD3‐induced CD4 + T‐cell proliferation but failed toaffect IL‐2 expression by anti‐CD3‐activated CD4 + T cells. PI3‐K inhibition during CTL induction resulted in decreased levels ofmRNAs coding for granzyme B, perforin, and Fas ligand. In addition, CTLinduced in the presence of PI3‐K inhibitors failed to conjugatenormally with P815 target cells. Exogenous IL‐2 did not reverse theeffects of PI3‐K inhibition on CD8 + T‐cell proliferationand CTL induction. These results support the conclusion that PI3‐Kactivation is involved in T‐cell receptor, CD28, and IL‐2 receptorsignaling of CD8 + T cells. PI3‐K is, therefore, animportant component of multiple signal transduction pathways involvedin CTL generation.