Resistance of G mice to murine leukemia virus infection: apparent disparity in in vivo and in vitro resistances.

We observed a marked discordance between in vivo and in vitro sensitivities to Friend murine leukemia virus in G mice. In vivo resistance of G mice was more than 10(5)-fold relative to sensitive DDD mice, whereas in vitro resistance was only 50 to 100-fold. In vivo sensitivity to N- and NB-tropic Friend murine leukemia virus was recessive in (G X DDD)F1 mice, whereas in vitro sensitivity was dominant in the heterozygotes. The resistance of mouse fibroblasts was different from the resistance of fibroblasts of a certain NZB mouse strain.