Natural killer (NK) cells and interferon in Friend-virus-infected susceptible and resistant mice.

Natural killer (NK) cells, as determined by the lysis of YAC-1 and Eveline target cells, were determined in F-MuLV-P susceptible DBA/2 and resistant C57/Bl/6 and in beige mice. No difference was found between DBA/2 and C57/Bl/6 mice. Spleens from beige mice showed, as expected, a much lower lysis. The NK cell activity and interferon levels were also studied in these mice after F-MuLV-P infection. Peak NK activities of spleen cells against both target cell types were found at day 3; peak interferon levels were detected in the serum 24 h after infection in all three strains. At day 12, the splenic NK cell activity remained above control levels only in C57/Bl/6 mice. Beige mice were as resistant to Friend leukemia development as C57/Bl/6 mice. The injection of endotoxin, which makes C57/Bl/6 mice virus-susceptible, was followed by increased NK cell activity. The significance of the NK cell system for the resistance of C57/Bl/6 mice against the development of Friend leukemia is discussed.