Early transmembrane events in alloimmune cytotoxic T-lymphocyte activation as revealed by stopped-flow fluorometry.

We have studied early transmembrane events in mouse alloimmune cytotoxic T-lymphocyte (LC7, H-2b) activation by specific target cells (mouse mastocytoma P815, H-2d) and a mitogenic lectin, Con A, by using stopped-flow fluorometry with three different fluorescent probes. After binding to target cells (P815), cytotoxic T lymphocytes (LC7) first increased their membrane fluidity and, then, calcium was released from intracellular stores. After that, there was a calcium influx from the external medium into the T lymphocytes. This calcium influx was blocked by calcium antagonists (verapamil or diltiazem). The same sequence of events was also observed in the activation of T lymphocytes (LC7) by Con A and in the response of specific target cells (P815) after cytotoxic T lymphocytes (LC7) binding. Nonspecific (syngeneic) target cells (mouse lymphoma EL-4, H-2b) did not cause any early transmembrane events in cytotoxic T lymphocytes (LC7, H-2b).