[Specific reactivity of semi-allogeneic chimeras produced using cyclophosphamide].

Specific immunological reactivity of semiallogeneic chimeras was studied. Long-lasting chimerism of lymphoid tissue was produced in CBA mice by intravenous injection of 10(8) spleen cells of (CBA X C57BL/6)F1 hybrids 3-6 hours after intraperitoneal administration of 200 mg/kg body weight of cyclophosphamide. Long-lasting specific acceptance of C57BL/6 skin grafts was observed in chimeras when skin was transplanted 2.5 and 4 months after tolerogenic treatment. Chronic rejection of skin grafts was more frequent in the latter case. The intensity of delayed type hypersensitivity reaction in chimeras was decreased in case of C57BL/6 antigens, but remained unchanged in case of BALB/c antigens. In the course of 0.5-6 months all the chimeras revealed specific areactivity of T-lymphocytes in respect to donor transplantation antigens in mixed lymphocyte culture. The level of the local graft-versus-host reaction was specifically decreased when lymphocytes of the chimeras were transplanted into the (CBA X C57BL/6)F1 hybrids 2.5-3.5 months after chimerism was induced. Thus, the results obtained demonstrate complete or partial areactivity to histocompatibility antigens of C57BL/6 strain in chimeric F1----CBA mice.