Isolation of two immunoglobulin G subclasses, IgG2 and IgG1, from hamster serum using protein A-sepharose

The isolation of hamster immunoglobulin classes and subclasses by affinity chromatography on protein A and selective elution was studied using 0.1 M phosphate buffer, pH 8. The IgG fraction was completely absorbed, while IgM did not bind. Sequential application of buffers of decreasing pH allowed the elution of pure IgG2 (eluted at pH 6) and IgG1 (eluted at pH 5). Both subclasses were fully recovered. IgG2 could be subfractionated into 2 peaks eluted respectively at pH 6.5 and 6. Immunodiffusion of the whole IgG2 fraction against anti-hamster immunoglobulin serum gave 2 precipitation lines. One of these lines was missing in the pH 6.5 fraction. Until now only 2 IgG subclasses have been described and these results suggest heterogeneity of hamster IgG2.