Isolation and Physico-Chemical Characterization of the “IgM-Like” Immunoglobulin from the Stingray Dasyatis Americana

Abstract

Abstract The stingray Dasyatis americana was found to synthesize high molecular weight antibodies against Salmonella typhosa “H” antigen and human A erythrocytes. These antibodies were demonstrated to be macroglobulins with a sedimentation coefficient of 17.1S and a molecular weight of 820,000. Carbohydrate analysis revealed a total content of 9.3% and a composition which was distinctively different from human IgM. Complete reduction and alkylation of the stingray macroglobulin, followed by gel filtration in the presence of guanidine hydrochloride, resulted in separation of the heavy (H) and light (L) polypeptide chains. These chains were found to have molecular weights of 70,000 and 23,000 for the H and L chains, respectively. With the exception of a lower content of the basic amino acids, the amino acid composition of the H and L chains was similar to that reported for human macroglobulin polypeptide chains. The stingray macroglobulin was examined by electron microscopy and displayed a pentameric structure. The data suggest a structural similarity between stingray macroglobulin and mammalian IgM.