Agglutination of mouse erythrocytes by binding of non-choline phospholipids to A 70 000-Dalton protein

Abstract

The structure of some phospholipids that cause agglutination of mouse erythrocytes has been studied. Haemagglutination is a property of non-choline-containing phospholipids; the phosphate group is essential and unsaturated fatty acids optimal. A protein of M r 70 000 was isolated from mouse erythrocyte membranes which completely inhibited phospholipid-mediated erythrocyte agglutination. It is proposed that this protein is the phospholipid binding site on mouse erythrocytes and the ligand for the human B-lymphocyte receptor for mouse erythrocytes. Preliminary investigations suggest that a similar inhibitor of phospholipid-mediated agglutination is found in serum. Agglutination of mouse erythrocytes by phospholipid and specific inhibition by the 70 kDa membrane protein constitute a simple system for studying the interaction of phospholipid with protein.