THE EFFECTS OF RM-CSF AND RIL-6 THERAPY ON IMMUNOSUPPRESSED ANTIORTHOSTATICALLY SUSPENDED MICE

Antiorthostatically suspended mice had suppressed macrophage developme nt in both unloaded and loaded bones, indicating a systemic effect. Bo ne marrow cells from those mice secreted less macrophage colony-stimul ating factor (M-CSF) and interleukin-6 (IL-6) than did control mice. B ecause M-CSF and IL-6 are important to bone marrow macrophage maturati on, we formulated the hypothesis that suppressed macrophage developmen t occurred as a result of the depressed levels of either M-CSF or IL-6 . To test the hypothesis, mice were administered recombinant M-CSF or IL-6 intraperitoneally We showed that recombinant M-CSF therapy, but n ot recombinant IL-6 therapy, reversed the suppressive effects of antio rthostatic suspension on macrophage development. These data suggest th at bone marrow cells that produce M-CSF are affected by antiorthostati c suspension and may contribute to the inhibited maturation of bone ma rrow macrophage progenitors.