Immunochemical studies of organ and tumor lipids XVIII. Cytolipin R determinants in the rat erythrocyte membrane.

Rabbit antisera to rat lymphosarcoma contain antibodies that agglutinate trypsinized rat erythrocytes. These reactions can be specifically inhibited by cytolipin R, a ceramide tetrasaccharide isolated from rat lymphosarcoma. The agglutinin in the rabbit antisera can be absorbed with untreated erythrocytes, showing that cytolipin R determinants are present in the intact rat erythrocyte membrane. Untreated erythrocytes are able to react with antibody, but presumably the number of cytolipin R determinants necessary for agglutination becomes available only after treatment with trypsin. The anti-cytolipin R antibodies in anti-rat lymphosarcoma sera that cause hemagglutination and those that fix complement with this hapten are different, since the agglutinin can be absorbed completely without appreciable decrease in complement-fixing antibody.