The rapid activation of cPKCβII by progesterone results in the negative regulation of Ca 2+ influx in human resting T cells.

Background: Progesterone-stimulated rapid suppression of phytohemagglutinin (PHA)-activated sustained membrane Ca 2+ influx is revealed by Mn 2+ quenching fura-2 fluorescence. Ca 2+ influx suppression results in immunosuppression of T-cell proliferation. Downregulation of protein kinase C (PKC) activity by phorbol 12-myristate 13-acetate (PMA) enhances the PHA-activated increase in sustained intracellular Ca 2+ concentration ([Ca 2+ ] i ) via Ca 2+ influx in T cells.