Abstract
Summary Peritoneal exudates were produced in guinea pigs by intraperitoneal injection of ferritin in previously immunized animals. The centrifuged cells of the exudate examined with the electron microscope were found to contain 10–15% eosinophils. Ferritin-antibody complexes, characteristic of in vitro immune complexes were observed within the cytoplasm of eosinophils and other granulocytes. This observation indicates that eosinophilia is mediated by immune complexes and provides evidence that at least one function of the eosinophil is the phagocytosis of antigen-antibody complexes. Our results showed no evidence that eosinophils are implicated in the formation of antibody.