Addition of monoclonal antibodies (UCHT1) directed against the antigen receptor/CD3 complex or the addition of the mitogens concanavalin A or phytohemagglutinin to human T lymphoblasts induced an elevation of the cytosolic free calcium concentration ([Ca2+]i) as monitored by the fluorescence of the intracellular fura-2. The rise in [Ca2+]i induced by these agents was effectively inhibited by staurosporine, an agent which inhibits protein kinase (PK)C and PKA. Conversely the PKC activator 12-O-tetradecanoyl phorbol-13-acetate decreased the delay and accelerated the rate of elevation of [Ca2+]i induced by the mitogens and UCHT1. Increasing the concentration of cAMP or cGMP in the T lymphoblasts had no effect on agonist-induced elevation of [Ca2+]i. Our data indicate that PKC can exert a positive feedback on the level of cytosolic Ca2+ in T lymphocytes, in contrast to what has been observed with other cells.
- T lymphocyte