MACROPHAGE SUPPRESSION OF GRANULOCYTE AND MACROPHAGE GROWTH FOLLOWINGBURN WOUND-INFECTION

Burn injury results in alterations in granulocyte and macrophage produ ction. Since macrophages may mediate these alterations we determined t he effects of macrophages obtained from animals with burn injury with and without infection on the growth of marrow granulocyte macrophage p rogenitor cells (GM-CFCs). The in vitro GM-CFC growth response for max imally stimulated cultures was reduced by 25% to 30% (p < 0.01) for bu rned and infected (B + I) animal macrophages compared with burned (B) or sham (S) animals. Macrophages stimulated with endotoxin caused a fu rther reduction for all groups in GM-CFC growth, most notably so for B + I macrophages. Burned + infected animal macrophages or allendotoxin macrophages cocultured with indomethacin did not suppress GM-CFC grow th. Following burn injury and infection, macrophages spontaneously ela borate negative regulators of myeloid growth that is further increased by endotoxin. It is likely that PGE(2), a known negative regulator of granulocyte macrophage growth, is largely responsible for this suppre ssive effect.