Studies on subunit components of immunoglobulin M from a bony fish, the chum salmon (Oncorhynchus keta)

Immunoglobulin M (IgM) was isolated from serum of the chum salmon (Oncorhynchus keta) by means of ion-exchange chromatography followed by gel filtration. The purified chum salmon IgM had a mol. wt of 730,000 and a tetrameric structure. However, a fraction of tetrameric IgM was considered to be non-covalently associated molecules. The amino acid composition was determined for the chum salmon micro-and L-chains and was found to be similar to that reported for other teleost fish micro- and L-chains. No J-chain- like component could be identified in the salmon IgM by either alkaline urea polyacrylamide gel electrophoresis or by the immunological cross-reaction with antisera to the human and chicken J-chain. The immunoglobulin cross-reactivity between the chum salmon micro-chain and that of 22 other fishes was tested, and only micro-chains from the family Salmonidae revealed cross-reactivity.