Antigen-specific T cell activation results in an increase in cytoplasmic free calcium.
Free intracellular calcium acts as a messenger in response to extracellular stimuli, including those that result in cellular proliferation. For example, mitogenic lectins have been shown to increase intracellular calcium concentration ([Ca+2]i) during proliferation of T lymphocytes. To determine if similar changes in [Ca+2]i occur when T cells are activated by nominal antigen, [Ca+2]i was measured in murine T cells from a bovine insulin-specific, major histocompatibility-restricted T hybridoma by using the calcium-sensitive fluor quin-2. Quin-2-loaded T hybridoma cells were activated by incubation with antigen-pulsed antigen-presenting cells (APC) and [Ca+2]i determined by measurement of quin-2 fluorescence. T cell [Ca+2]i rose sharply within 20 min after incubation with APC. Incubation of T cells with unpulsed APC resulted in [Ca+2]i not significantly different from resting levels. Further evidence that this activation was antigen specific was demonstrated at the level of both the APC and the T cell. Incubation of quin-2-loaded T cells with APC pulsed with the inappropriate antigen, porcine insulin, did not result in an increase in [Ca+2]i. Additionally, pretreatment of T cells with a monoclonal antibody against the T cell antigen receptor abrogated the [Ca+2]i increase. Finally, the antigen-induced rise in [Ca+2]i could be blocked by pretreatment of APC with appropriate but not inappropriate Ia monoclonal antibodies. These results suggest that a rapid rise in [Ca+2]i is an early event in the antigen-specific activation of the T cell and may be related to later steps, such as the secretion of lymphocyte monokines.
D N
DN
Shapiro
B S
BS
Adams
J E
JE
Niederhuber
D000818:Animals; D000911:Antibodies, Monoclonal / Q000502:physiology; D001667:Binding, Competitive; D002118:Calcium / Q000096:biosynthesis*; D002417:Cattle; D002474:Cell-Free System; D004533:Egtazic Acid / Q000494:pharmacology; D000939:Epitopes; D006825:Hybridomas / Q000276:immunology / Q000378:metabolism; D007328:Insulin / Q000276:immunology; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D051379:Mice; D008806:Mice, Inbred AKR; D013552:Swine; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000939:Epitopes; D007328:Insulin; D007376:Interleukin-2; D004533:Egtazic Acid; D002118:Calcium