Phagocytosis of horse erythrocytes treated with equine infectious anemia virus by cultivated horse leukocytes.

Horse erythrocytes treated with equine infectious anemia virus hemagglutinin were phagocytized by cultivated horse leukocytes (mainly macrophage-like cells and partly polymorphonuclear cells) after incubation with fresh horse serum but not with inactivated horse serum. The phagocytosis began as soon as the erythrocytes were added to the leukocyte cultures, and the majority of the reaction proceeded within 30 minutes. Addition of antiserum showed a slightly suppressing but no enhancing effect on the phagocytosis. Phagocytosis seemed to be caused by the recognition of the third complement component on the affected RBC with the receptors on phagocytes, but not by the recognition of immunoglobulin. Since cultivated leukocytes were able to phagocytize erythrocytes which were treated with a quantity as small as 1/16 units of hemagglutinin, and since the hemagglutinin-antibody complex also could bind to erythrocytes and induced them to become phagocytized, the reaction appears to play an important role in the mechanisms of anemia and formation of sideroleukocytes in horses infected with the equine infectious anemia virus.