Effects of Friend leukemia virus (FLV) inoculation in F1 mice and differentiation of FLV-induced leukemia.

Effects of Friend leukemia virus (FLV) inoculation in F1 specific pathogen free (SPF) mice were examined. Resistance to FLV was dominantly inherited both in F1 hybrid mice (BDF1) (FLV-resistant & FLV-sensitive with polycythemia) and F1 hybrid mice (B6C3F1) (FLV-resistant & FLV-sensitive with anemia). But the population dynamics of the nucleated cell components of F1 mice after FLV inoculation differed from those of FLV-resistant inbred mice. A small number of mature erythroblasts appeared in the peripheral blood of BDF1 mice. In B6C3F1 mice, erythroblastosis with splenomegaly and polycythemia occurred. However, all of these findings in BDF1 and B6C3F1 mice regressed spontaneously. In F1 mice, FLV induced an intermediate reactive pattern of the two patterns that had been induced in the parental strains. The results indicate that FLV may induce leukemia with various degrees of differentiation, according to the genetic difference of the host.