Regulation of CFU-S proliferation by locally produced endogenous factors.

The presence of proliferating and non-proliferating CFU-S in, respectively, the bone marrow and spleens of phenylhydrazine (PHZ) treated mice has afforded the opportunity to investigate the presence and role of local factors responsible for the control of CFU-S proliferation. When bone marrow cells from PHZ treated mice are incubated with irradiated spleen cells taken from the same mice, there is a marked fall in the proportion of femoral CFU-S in DNA synthesis. In the converse experiments rapid triggering of splenic CFU-S is achieved. Changes in CFU-S proliferation have also been demonstrated in other situations where cell populations containing proliferating and minimally proliferating CFU-S are mixed.