Cation requirement of natural, in-vitro generated and antibody dependent killing exerted by human lymphocytes

Three cytotoxic systems, NK, ADCC and the seemingly indiscriminative cytotoxicity of in vitro activated lymphocytes (cultivated with K 562) were found to require Ca++ and did not function in Mg++. The optimum concentration of Ca++ was identical for the three systems and for various lymphocyte subsets. 15 minutes after initiation of the interaction cell damage had already occurred in all three systems.