Functional roles of ion channels in lymphocytes

The application of patch-clamp and video-imaging techniques has enabled responses of lymphocytes to be examined at the level of individual cells. Eight distinct types of ion channel activity have been revealed in T lymphocytes. A variety of external stimuli shifts the pattern of channel activity from the resting state, which is dominated by voltage-gated K+ channels. Channel regulation is achieved both by acute modulation and by altered expression in the membrane. During mitogen stimulation, Ca2+ channels and Ca(2+)-activated K+ channels become active and appear to underlie Ca2+ oscillations. These acute changes are followed by increased expression of voltage-gated K+ channels. In response to osmotic challenge in hypotonic media, cell swelling initiates activation of Cl- channels, which may, in turn, indirectly activate K+ channels and trigger a regulatory decrease in cell volume.