Natural cell-mediated cytotoxicity in the domestic cat: properties and specificity of effector cells

Using a 51Cr-release microcytotoxicity assay, natural cytotoxic cell activity was demonstrated in the peripheral blood of clinically normal, nonimmune cats. Cytotoxicity was enhanced against virus-infected feline cells over that in noninfected cells. Xenogeneic mouse and hamster target cells were also susceptible to lysis. The cytotoxic activity increased as effector-to-target cell ratios were increased and required a 16-hour assay to be expressed. The specificity of the natural cytotoxicity was selective in that some, but not all, target cells tested were susceptible to lysis. Characterization of the cytotoxic cells showed them to be nonadherent and to possess Fc receptors for immunoglobulin G.