The immunoglobulins of carcharhine sharks: a comparison of serological and biochemical properties.

The immunoglobulins of three carcharhine sharks were isolated from serum by means of salt precipitation and gel chromatography. The Galapagos shark (Carcharhinus galapagensis), the sandbar shark (Carcharhinus plumbeus) and the tiger shark (Galeocerdo cuvieri) each contained high molecular weight (18S) and low molecular weight (7S) IgM-like molecules as the major serum immunoglobulins. Both within and between species 18S and 7S immunoglobulins closely resemble each other in antigenic character, polypeptide chain composition, chain mass, amino acid composition, carbohydrate content and amino-terminal sequence. These results suggest that the immunoglobulins of carcharhine sharks have undergone little structural divergence during their evolution.