Cytophilic antibody. I. Nature of the macrophage receptor.

Cytophilic antibody was produced in guinea-pigs by single injections of sheep erythrocytes in Freund's complete adjuvant. The nature of the receptor for this antibody was studied by treating macrophages with various reagents and determining changes in their ability to take up cytophilic antibody, as shown by the subsequent adherence of sheep red cells. Receptor activity was destroyed by phospholipase A, iodine and periodate: it was reduced by lanthanum and uranyl ions, but not by calcium ions, although all these ions are able to interact with lipids. It was also reduced by poly-L-lysine. The receptor was not affected by pH in the range 5.4–9.0 or by the presence of EDTA, heparin, chloroquine or hydrocortisone. Neuraminidase and lipase had little effect but preteolytic enzymes appeared to increase the uptake of cytophilic antibody. It was concluded that a phospholipid or phospholipoprotein is an important part of the macrophage receptor for cytophilic antibody.