Voltage-gated potassium channels are required for human T lymphocyte activation

The involvement of ion channels in T lymphocyte activation is suggested by reports of membrane depolarization (1-3), hyperpolarization (2, 4), increased ion fluxes across the membrane (5-9), and increased intracellular f ee calcium (4, 10) after mitogenic stimulation. Furthermore, various tages of T lymphocyte activation are inhibited by substances known to block ion channels in other tissues (11-15). Using the gigaohm seal recording technique (16), we and others (15, 17) recently demonstrated the existence in human T lymphocytes of a voltage-gated potassium (K) channel that resembles delayed rectifier K channels of nerve and muscle. There are ~200-300 channels in each T lymphocyte (15, 18). The K channels open when the membrane is depolarized, but do not appear to be sensitive to levels of internal calcium (15, 18) known to activate the calcium-activated "maxi " K channel (19). Furthermore, calcium channels have not been detected (15, 17, 18); thus, the voltage-gated K channel appears to be the main channel in human T lymphocytes. Phytohemagglutinin (PHA) l is a potent mitogen of human T lymphocyte