Effects of calcium ionophore and phorbol ester on class-II-restricted virus-specific human cytotoxic T cell clones.

Calcium ionophore A23187 and phorbol myristate acetate (PMA) were studied for their functional effects on human class-II-restricted measles virus-specific CD4+ cytotoxic T lymphocyte (CTL) clones. A23187 and PMA each dramatically inhibited virus-specific CTL activity. Both PMA and A23187 induced proliferation of resting clones and augmented relatively weak or suboptimal proliferative responses, but inhibited vigorous antigen- or mitogen-induced proliferation. The parallel responses induced by these two agents suggest that they produce their effects via similar mechanisms, most likely through protein kinase C.