Secondary cytotoxic cell response to lymphocytic choriomeningitis virus II. Nature and specificity of effector cells.

The method described in the previous paper was used to induce secondary responses in spleen cells from CBA/H mice, pre-primed with lymphocytic choriomeningitis (LCM) virus by culturing them with LCM-infected peritoneal cells. The cytolytic effector cells thus generated have been characterized. Effector cells were sensitive to treatment with anti-theta ascitic fluid and complement. Separation procedures based on rosetting of certain categories of lymphocytes with sheep red cells through an Isopaque-Ficoll gradient indicated that effector cells lacked surface immunoglobulin and generally did not bear Fc receptors. Cytolytic activity was restricted by the H-2 gene complex. Killing had single-hit characteristics. All these results suggested that the cells from memory cultures mediating cytolysis were T cells. There was evidence for two T cell subsets, a major subpopulation directed against antigens on infected targets and a minor one directed against antigens on uninfected, H-2-compatible targets. Specificity was present at the infected cell:memory responder and killer:target levels between LCM virus (an arenavirus) and ectromelia virus (a poxvirus).