Inositol lipid metabolism in human T lymphocytes activated via the T3 complex

Cloned human T lymphocytes and a mitogenic monoclonal antibody (UCHT1) that binds to the T3 antigen complex were used to study the role of inositol lipid hydrolysis in T-cell activation. Binding of the T3 molecular complex with anti-T3 antibody induced the generation of inositol trisphosphate after a lag of 1 min. While this is commensurate with the rise in cytosolic Ca2+ in these cells, examination of the inositol lipid revealed that phosphorylation of phosphatidylinositol 4-phosphate to phosphatidylinositol 4,5-bisphosphate occurred before the generation of inositol trisphosphate. Thus, activation of an inositol lipid kinase appears to be one of the primary signals in cellular activation in human T lymphocytes.