Isolation and partial characterization of immunoglobulin from a urodele amphibian (Necturus masculosus)

Abstract

The primitive amphibian species, Necturus maculosus, a urodele, possessed serum immunoglobulin characterized by a mol. wt of approximately 900,000. Upon reduction of disulphide bonds and analysis under dissociating conditions, this molecule was resolved into polypeptide chains resembling light chains and μ-type heavy chains and having mol. wt of 22,000 and 70,000 respectively. The Necturus immunoglobulin was antigenically related to the IgM-like immunoglobulins of the toad (Bufo marinus) and the Xenopus. Unlike these anuran amphibians, however, the Necturus did not possess detectable amounts of low molecular weight immunoglobulins.

The finding raises the evolutionary possibility that the γ-like heavy chains of advanced amphibians may represent the results of a gene duplication independent of that which was responsible for the emergence of the γ heavy chain of mammals.