[Hemopoietic action of the high-molecular fraction of leukocytic pyrogen]

During fractionation of the rabbit leukocytic pyrogen (LP) on Sephadex column and by the ethanol method, the apyrogenic protein fraction was isolated. In intact rats this fraction induced granulocytopoiesis stimulation: a rise in granulocyte proliferative activity, an increase in total granulocyte count in the bone marrow and peripheral blood, and also a rise in the number of macrocolonies in the spleen of lethally irradiated mice due to an increase in granulocyte colonies.