Serum potentiation of granulocyte and macrophage colony formation in vitro

Addition of serum or plasma from many species increased the number and size of neutrophilic granulocyte and macrophage colonies formed in vitro by mouse bone marrow cells after stimulation by a variety of preparations containing colony stimulating factor (CSF). The active factor in serum was heat-labile, non-dialyzable and eluted from G-100 columns in the serum albumin region. Serum non-selectively affected all cells potentially capable of forming granulocytic and macrophage colonies but did not potentiate the formation of eosinophilic or megakaryocytic colonies. The potentiating activity of mouse serum was increased by prior injection of the mice with endotoxin but was not affected by prior whole-body irradiation. Colony potentiating activity in plasma from patients with myeloid of lymphoid leukemia did not differ from that of normal human plasma.