The role of eosinophil in regulation of granulopoiesis.

An association between eosinophilia and neutropenia has been observed in a number of clinical conditions. To probe the role of eosinophils in granulopoiesis, marrow and peritoneal eosinophils, obtained from Schistosoma mansoni-infected mice, were separated and purified. Normal bone marrow cells were cultured in semi-solid culture medium in concentrations ranging from 5 X 10(4) to 5 X 10(5), with and without added eosinophils. To examine whether high prostaglandin E (PGE) content of eosinophils affects granulopoiesis, indomethacin was added to duplicate marrow cultures containing eosinophils. The addition of eosinophils to normal syngeneic marrow culture caused a significant inhibition of granulocyte-macrophage colony formation (CFU-GM) in culture. This suppressive effect was reversible upon addition of indomethacin. These findings suggest that eosinophils, in vitro, are capable of inhibition of granulopoiesis. The reversal of this effect by indomethacin indicates that this suppression may be prostaglandin mediated.