Spatial and temporal characteristics of the increase in intracellular Ca2+ induced in cytotoxic T lymphocytes by cellular antigen.

The increase in intracellular Ca2+ concentration [( Ca2+]i) in cytolytic T lymphocytes in response to target cell binding was investigated by ratio image fluorescence microscopy. Ca2+ mobilization from intracellular stores occurred at a site distal to target cell contact and was transient. Extracellular Ca2+ influx resulted in an increase in [Ca2+]i that was prolonged and distributed more proximal to the target cell. Oscillations in [Ca2+]i were observed after target cell contact, although the periodicity was dependent on the presence of extracellular Ca2+. The Ag-specific reorientation of cytoplasmic granules occurred well after [Ca2+]i had begun to decline to a resting level, but was dependent on extracellular Ca2+. These studies indicate that the Ag-stimulated increase in [Ca2+]i exhibits considerable spatial and temporal variation, and that these characteristics are altered by the availability of extracellular Ca2+. The results also suggest that these changes in [Ca2+]i may play a role in the cytoplasmic events that accompany T cell-mediated cytolysis.