STIMULATOR OF PROLIFERATION OF SPLEEN COLONY-FORMING CELLS IN ACUTE STERILE INFLAMMATION

The presence and activity of a spleen colony-forming cell (CFU-S) prol iferation stimulator was investigated in rat bone marrow after inducti on of sterile inflammation. Wistar rats were treated intraperitoneally with two 15 ml injections of 3.5% polyvinylpyrrolidone (PVP) at 18h i ntervals, and the presence of CFU-S proliferation stimulator determine d in bone marrow 6, 20 and 24h after the first injection. The marrow o f these mice was used to condition medium which was then fractionated using Amicon Diaflo ultrafiltration membranes. The 30-50 kDa fraction, taken from 20 h post-PVP-bone marrow extract, was found to induce cyc ling of d8-CFU-S in normal mouse bone marrow. This activity was not re lated to the presence of interleukins-1, -2 or -6 like activities in t he material tested. The results demonstrate the existence of CFU-S pro liferation stimulator in the bone marrow of rats with sterile inflamma tion (i.e. in an in vivo tissue response to non-specific cell stimulat ion), similar to that originally described as a macrophage product in mouse bone marrow after treatment with a variety of cytotoxic agents.