Cyclophosphamide-induced chimerism.

BALB/c mice were injected with cyclophosphamide (Cytoxan) (180-280 mg/kg) i.p., and with 3 X 10T (BALB/c 9 X DBA a ) Fj (CDF) spleen cells i.v. The recipients were bled periodically and their sera tested for DBA y-globulin. All mice had levels of donor y-globulin at 2 weeks; 17/24 still had detectable levels at 6 months. A greater proportion of mice had detectable donor y-globulin for a longer time and in higher titer when treated with the highest dose of Cytoxan. All mice received CDF skin grafts 2 weeks after Cytoxan and CDF spleen infusion. Marked prolongation of skin graft survival was observed. In general, skin graft rejection correlated well with loss of donor y-globulin. However, 4 mice which rejected skin grafts within one month continued to have detectable donor y-globulin for 6 months. The results are similar to those re ported for X-irradiation-induced chimeras.