Comparative studies of humoral factors stimulating granulopoiesis in agar in vitro and in diffusion chambers

The factor stimulating granulopoiesis in diffusion chambers (DCF) was compared with the CSA in post-EMS in two ways: (1) Mouse bone marrow cells were maintained in suspension cultures, containing DCF or EMS, which were assayed at intervals for colony-forming cells, both in agar in vitro and in diffusion chambers. (2) The enhanced growth seen in chambers incubated in pretreated mice was compared with the CSA of serum and DCF recovered from these animals. The results show that the cells forming granulocytic colonies in agar in vitro and in diffusion chambers are closely related, if not identical, and that different sources of CSA may differ in their ability to maintain precursor cell numbers in suspension culture. The CSA of DCF did not correlate with growth enhancement in diffusion chambers or with the levels of CSA in the serum.