Isolation, Purification, and Molecular-Weight Determination of Serum Immunoglobulin from<i>Oreochromis aureus</i>

Abstract

Techniques for the isolation and purification of serum immunoglobulin (Ig) from fish are presented. By inducing a specific fish antibody and purifying the antibody by affinity chromatography, the major Ig class of an economically important group of fish was partially characterized. Immunoglobulin of an IgM-like class from the serum of a tilapine fish, Oreochromis aureus, was determined to have a molecular weight between 780,000 and 788,000. After the O. aureus serum Ig was reduced, the molecular weight of its heavy chain was estimated by means of electrophoretic analysis (SDS-PAGE) to be about 77,000, and its distinct light chains had estimated molecular weights of 21,500 and 20,500. Rabbit antiserum to the affinity-purified O. aureus serum Ig did not react with sera from distantly related species of fish, including rainbow trout Oncorhynchus mykiss, largemouth bass Micropterus salmoides, channel catfish Ictalurus punctatus, striped bass Morone saxatilis, goldfish Carassius auratus, and some Central and South American cichlids; however, the Ig did cross-react with sera from more closely related African cichlids, including some species in the genera Oreochromis, Haplochromis, and Pseudotropheus