The enhanced colony growth of mouse CFU-c by human serum.

The addition of human serum to colony stimulating factor (CSF) enhances the growth of granulocyte and macrophage colonies derived from C57 BL/6 mouse marrow cells. The growthenhancing effect of normal human serum was dose-dependent and observed in various colony assay systems employing conditioned medium prepared from L-cells, human peripheral blood leukocytes, C BL/6 mouse whole embryo and sera from C BL/6 mice injected with E. coil endotoxin. The enhancing activity was also shown in sera of mice, rats and rabbits but not in those of guinea pigs and fetal calves. The enhancing activity of sera from patients with various hematological diseases, so far assayed, does not significantly differ from that of normal control sera. The active principle in human sera was heat-stable, non-dialysable, not extractable by ether and separated in the lower molecular weight zone corresponding to albumin and Ig G by gel filtration of Sephadex G-200. Neither pure human albumin nor Ig G showed any enhancing effect on the colony formation. On the other hand, gel filtration of normal human serum on Sephadex G-200 demonstrated the inhibitory component of the colony growth in the higher molecular weight zone corresponding to Ig M. As the pretreatment of marrow cells with the active principle in human sera did not show any effect on the colony growth and the coexistence of the active principle in human sera and CSF was required for the enhanced colony growth, the cooperative action of the active principle in human sera and CSF is thought to be required for the enhancement of the colony growth.