Leucopoiesis versus concentration of cytokines in diffusion chamber cultures of mouse bone marrow cells: clues to the physiological roles of growth factors.

Abstract

Physiological mechanisms that regulate formation of neutrophil granulocytes, macrophages and their precursor cells were studied with the diffusion chamber (DC) technique. DC inoculated with mouse bone marrow cells were implanted intraperitoneally into host mice. When these in vivo cultures had been established and their marrow populations were expanding (2-day cultures), the DC were transferred to different environments: new, normal mice, lethally irradiated mice, or incubation flasks with optimal concentrations of growth factors. Culture development during the following final culture period was correlated to the concentration of some select candidate growth regulators in DC. After 3 d the cellularity of DC in irradiated hosts had increased significantly more than in the normal hosts. A difference was detectable already after 1-2 d when preculturing was omitted. The increased growth appeared to take place at several stages of cell maturation and not only at the progenitor cell level. Colony stimulating factor(s) for granulocyte and macrophage progenitors, as well as cytokines stimulating the bone marrow-derived cell line, 14 M.1, were present in DC fluid (DCF) at higher concentrations in irradiated than in normal mice throughout the final culture period. On the other hand, DCF concentrations of tumour necrosis-like factor (that may either induce CSF secretion or directly inhibit myelopoiesis), were not significantly different in irradiated compared with normal DC hosts. The cytokines detected in the DC may at least in part stem from inflammatory cells accumulating around the chambers. This animal model should be useful in further investigation of the highly complex regulatory network governing formation of white blood cells in the intact organism.