Intracellular Calcium and Protein Kinase C Regulate Nonspecific Cell-Mediated Cytotoxicity by Mouse Lymphocytes (Calmodulin)
The role of Ca('2+) and other stimulus-response couplers in lymphocyte-mediated cytotoxicity was examined through the use of various pharmacological agents. The calcium ionophore A23187 caused a marked increase in nonspecific cytotoxicity by mouse spleen lymphocytes against SV3T3 target cells. Using a standard ('51)Cr-release assay, little target cell death was seen prior to 16 hours of effector-target incubation. The kinetics of the ('51)Cr-release were not changed by addition of A23187. Both uninduced and ionophore-induced lysis was suppressed by the Ca('2+) channel blocker verapamil, inhibitors of calmodulin, and agents which increase cAMP levels. TPA, a tumor promoting phorbol ester, also enhanced nonspecific cytotoxicity, suggesting a role for protein kinase C in cytotoxicity. TPA and A23187 caused a synergistic increase in cytotoxicity when added together. A23187 also enhanced the cytotoxic activity of lymphocytes from nude and beige mouse spleens. Spleen cell populations in which Qa 5('+) and Thy 1.2('+) populations had been inactivated were much less affected by A23187 treatment. Lysis of the lymphoma target YAC-1 was also tested in the presence of A23187. Although uninduced lysis of YAC-1 cells is normally seen in a 4-hour assay, enhancement of cytotoxicity by the ionophore required a 16-hour assay to see an effect, as when SV3T3 targets were used. The only exception to this was the observation that A23187 enhanced the cytotoxic activity of beige mouse lymphocytes against YAC-1 cells in a 4-hour assay, suggesting that the ionophore could reverse the defect in natural killer cell activity which is characteristic of beige mouse lymphocytes. Together, the results suggest that Ca('2+) influx augments lymphocyte-mediated cytotoxicity by acting as an intracellular messenger, and that it either directly stimulates the cytotoxic process or causes enhanced release of lymphokines which stimulate cytotoxic cells to higher levels of activity.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign