The role of eosinophils in granulopoiesis. I. Eosinophilia in neutropenic patients.

The role of eosinophils in granulopoiesis is unclear. In a variety of conditions, the level of eosinophils is inversely related to the level of neutrophils. The present report describes two patients with eosinophilia and neutropenia and examines the in vitro effects of eosinophils on the colony formation of their bone marrow in semisolid culture medium. The addition of autologous eosinophils to bone marrow cultures from these patients resulted in a decrease in the number of colonies; in contrast, antieosinophilic serum increased the number of colony-forming units. Indomethacin, an inhibitor of prostaglandin, was capable of reversing the effects of added eosinophils. The findings suggest that eosinophils have an inhibitory effect on in vitro granulopoiesis. The suppressive effects may be due to the high content of prostaglandin E found in eosinophils. A schematic diagram based on the current knowledge of the mechanism of granulopoiesis is presented.