Biological and Chemical Properties of Natural Antibodies in the Nurse Shark

Abstract

Immunoglobulin was purified from serum of the nurse shark by gel filtration and ion exchange chromatography. The purified immunoglobulin was used in a mixed agglutination assay by sensitizing chicken or pigeon erythrocytes and reacting the sensitized cells with unsensitized erythrocytes from other species. Strong positive reactions were obtained with erythrocytes from several species. Further studies revealed the presence of a natural antibody to DNP. The antibody activity was associated primarily with 19S immunoglobulin and was characterized by low affinity. Although it did not bind to a DNP immunoadsorbent, it could be adsorbed following precipitation with DNP-BSA (bovine serum albumin). Enzymatic digestion yielded 5S subunits which showed the same DNP-binding activity as the intact molecule. Antibody purified by precipitation with DNP-BSA was found to agglutinate red blood cells and bind guanosine monophosphate.