Abstract
Lymphocytic choriomeningitis virus (LCMV) infection of C3H/St, nude (BALB/c background), and other mice induced high levels of natural killer (NK) cell activity in the spleen and peritoneum. L-929 cells were used as targetsand were not lysed by spleen or peritoneal cells from uninfected mice. The cytotoxic cells were characterized as NK cells because they were nonadherent, nonphagocytic lymphocytes lacking θ and immunoglobulin antigens on their plasma membranes. Their activity was sensitive to 6 mM EDTA and to heating for 5 h at 37 degrees C, but resisted treatment with 0.5 percent trypsin. No role for antibody could be demonstrated in these assays. Relative to cytotoxic T-cell activity, the induction of NK cell activity was resistant to X-irradiation of mice with 1,000 rads but was sensitive if mice were first treated with Strontium-89, a bone-seeking isotope.