Effects of busulfan (BU) on hemopoiesis and immune reactivity in dogs.

Hematologic and immunosuppressive effects of BU were evaluated in 21 dogs. Twenty to 30 mg BU/kg produced severe but in most cases reversible myelotoxicity. All animals given 40 mg BU/kg died of marrow failure which was consistently reversed by the infusion of autologous marrow. Granulocytic progenitor cells (CFU-C) in the bone marrow of BU-treated dogs were severely depressed by day 7 after drug administration and in surviving animals showed only slow recovery to normal values. Cell-mediated immunity as determined by the in vitro reactivity of lymphocytes was normal after stimulation with T-cell mitogens (PHA, ConA), but impaired after stimulation with B-cell mitogens (PWM, SpA). Antibody formation against sheep red blood cells was not suppressed by BU-treatment.