Radiation and primary response to lipopolysaccharide: bone marrow-derived cells and susceptible organs

The major goal of this study was to determine whether radiation significantly alters bone marrow-derived cell distribution and mass of sensitive organs after challenge with lipopolysaccharide (LPS).

C57BL/6 mice were exposed whole-body to 0 or 3 gray (Gy) gamma-radiation (60Co) and injected intraperitoneally with 0.1 ml saline or 1 mg/kg LPS (E. coli serotype 0111:B4) 10 days later. Subsets from each group were euthanized at 60 min and 1, 7 and 14 days post-injection for analyses.

Body mass was low 1 day after LPS, especially in irradiated animals. LPS-induced splenomegaly and hepatomegaly were attenuated by radiation, whereas thymic atrophy was enhanced. However, radiation had no effect on LPS-induced changes in oxygen radical production by liver phagocytes. The numbers of all major leukocyte populations (lymphocytes, monocyte-macrophages, granulocytes) were altered by both radiation and LPS at virtually all time points of testing. In general, the LPS-induced changes in leukocytes were diminished by radiation. Significant radiation x LPS interactions were especially prominent at day 1 after LPS administration. In contrast, mice receiving both radiation and LPS had lower red blood cell (RBC) and platelet counts than those receiving either agent alone.

The data show that radiation had a highly significant influence on LPS-induced changes in mass of several body organs, leukocytes, RBC, and platelets, and thus may increase severity of infection due to Gram-negative bacteria.