STUDIES ON CYTOPHILIC ANTIBODIES

Summary Serum obtained seven days after immunization of Swiss mice with sheep erythrocytes in Freund's adjuvant contains a factor, with fast α 1 ‐globulin mobility, detectable by its ability to induce the attachment of sheep erythrocytes to normal mouse macophages. The receptor on macrophages is trypsin‐sensitive. The factor has a large degree of, though not complete, immunological specificity. It appears to be unrelated to conventional immunoglobulins. non‐agglutinating and non‐complement‐fixing. Subsidiary evidence consistent with the existence of an α‐globulin “antibody” and a consideration of its possible immunological significance are presented.