The role of colony stimulating activity in modulating murine diffusion chamber granulopoiesis

We studied the effects of high circulating Colony Stimulating Activity (CSA) levels and irradiation induced marrow hypoplasia in CF1 and C57B1/6J host mice upon granulopoiesis in intraperitoneal diffusion chamber (DC) cultures. Serial endotoxin injections resulted in marked elevation of circulating CSA for the first half of an 8 d culture period, and CSA was shown to diffuse into the chamber environment; yet this manipulation alone did not significantly accelerate DC cell growth. Pre-irradiation of the host mice produced no elevation of circulating CSA during the early phase of culture, but resulted in significant stimulation of DC granolopoiesis. Fluctuations in circulating inhibitors of in vitro granulopoiesis did not correlate well with DC cellularity. We conclude that endogenous CSA elevation does not providean effective stimulus per se for granulocyte-monocyte proliferation within DC culture and cannot be solely responsible for mediating the exuberant DC granulopoietic response seen in the pre-irradiated host.