Stimulatory effect of staphylococcal leukocidin on granulopoiesis disturbed by cytostatic agents.

Functional tests of granulopoiesis (leukocytosis, bone marrow picture, incubation in vitro of bone marrow with [3H]thymidine followed by radioautography and counting of labeled promyelocytes and myelocytes, serum muramidase level, liberation of granulocyte bone marrow reserve, Nitro-BT reduction in blood granulocytes, enzyme cytochemistry, and phagocytosis) were performed in rabbits given bubulphan (10 mg/kg) or 5-fluorouracil (200 mg/kg). Determinations were carried on serially during treatment with cytostatics. Some of the cytostatic-treated animals received intravenous (i.v.) injections of purified staphylococcal leukocidin in daily doses of 0.1 mg/kg. In control animals, theleukocidin resulted in stimulation of granulopoiesis (leukocytosis, increased number of [3H]thymidine-labeled myelocytes, elevated serum muramidase level). Animals receiving cytostatics suffered from marked inhibition of granulopoiesis accompanied by decrease of bone marrow granulocyte reserve. Injection of staphylococcal leukocidin during the period of myelosuppression evoked by cytostatics resulted in partial protection of granylopoiesis and faster regeneration of the leukocyte system.