Expression of Fv-4r allele in hematopoietic cells from G mice resistant to Friend leukemia virus.

G mice carrying the Fv-4r resistant allele supported virus growth neither at an early nor a later (Kai et al., 1976) stage of infection with NB-tropic FLV. This resistance could not be abolished by treatment of G mice with cyclophosphamide or cortisone acetate. By bone-marrow or spleen-cell transplantation into irradiated mice, the resistan-e of G mice could be transferred to Fv-4-susceptible mice. Conversely, transfer of bone-marrow or spleen cells of Fv-4-susceptible mice rendered G mice susceptible. It could be concluded that, as assessed by the virus content in the spleen, helper LLV grows mainly in radiosensitive, bone-marrow-derived cells, and the Fv-4 gene is expressed in these cells.