The effect of pretreatment of allogeneic bone marrow graft recipients with antilymphocytic serum on the acute graft-versus-host reaction in monkeys

Short-term pretreatment of irradiated, bone marrow-treated monkeys with horse antilymphocyte serum (ALS) roughly doubles the survival time by decreasing the severity and delaying the onset of acute secondary disease in random host-donor combinations. It was found that (1) horse anti monkey serum does not interfere with the take and proliferation of the graft, and that (2) rabbit anti monkey serum acts less selectively, as shown by a high incidence of transplant failures. The absence of signs of stem cell toxicity in monkeys treated with horse ALS cannot be attributed to a lower degree of immunosuppression, because lower doses of rabbit ALS are as toxic as larger doses. The use of ALS for pretreatment of human bone marrow recipients is recommended, but, for the time being, only horse serum should be used. The effective dose of horse ALS for monkeys is in the order of 60 mg of IgG/ kg body wt/ day. Pretreatment for 2 days seems to be adequate