Mechanisms of genetic resistance to Friend virus leukemia in mice. IV. Identification of a gene (Fv-3) regulating immunosuppression in vitro, and its distinction from Fv-2 and genes regulating marrow allograft reactivity.

Friend leukemia viru (FV) suppresses the proliferative response of normal lymphocytes to mitogens. The in vitro suppressive effect of FV on lymphocyte mitogenesis is mediated by T-suppressor cells and is under host genetic control. Lymphocytes from strains of mice of the C57BL background (e.g., C57BL/6) are resistant while cells from other strains (e.g., 129 and DBA/2) are susceptible. Genetic analyses utilizing resistant and susceptible parental strains, their F1, intercross and backcross progeny indicated that susceptibility to in vitro suppression is regulated by a single autosomal gene, dominant for susceptibility to suppression. This gene, which is not linked to the H-2 complex, segregated independently of the Fv-2 gene which controls resistance to spleen focus formation in vivo. The gene is also unlinked to the Ir-like genes which regulate the ability of H-2d mice to reject H-2b bone marrow grafts. The gene is therefore designated as Fv-3. Fv-3 may mediate its effect by regulating the numbers and/or functions of T-suppressor cells.