An agglutinin in the haemolymph of an ascidian promoting adhesion of sheep erythrocytes to mouse macrophages.

Sheep erythrocytes sensitized with subagglutinating doses of haemolymph from Botrylloides leachii were found to bind strongly to mouse peritoneal macrophages in vitro. Erythrocytes sensitized with similar agglutinating doses of plant lectins or haemolymph from the fresh water crayfish Cherax destructor did not adhere. The adherence promoted by B. leachii haemolymph appears to be a heteroagglutination reaction mediated by a molecule which binds to lactose-like determinants on both erythrocytes and macrophages.