Effect of bacterial lipopolysaccharide on proliferation of CFU-S.

Multiple injections of S. typhosa LPS increased the number of CFU-S in the spleen 20-50 fold and decreased the number in the femur to one half or less. LPS injections did not affect the growth rates of CFU-S in the spleen or femur of lethally irradiated mice. The plateau levels which were attained in these mice after proliferation, corresponded with the levels in LPS-treated non-irradiated mice. Local irradiation of the spleen with 3000 rad hardly affected the capacity of the spleen to accommodate the increased CFU-S numbers after LPS injection. These results suggest that irradiation resistant microenvironmental factors in the spleen determine the CFU-S accumulation in this organ after injection of Salmonella typhosa LPS. The increased number of CFU-S in the blood after LPS injection was maintained in splenectomized mice as well as in mice which received a local splenic x-irradiation with 3000 rad, indicating that this rise of blood CFU-S numbers is independent of the spleen.