Interactions between Mouse Immunoglobulins and Staphylococcal Protein A

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Abstract
When mouse serum or ascites is applied on protein A-Sepharose columns and washed with enough phosphate-buffered saline, a second protein peak is often eluted with the same buffer after the first major peak of unbound proteins. This second peak is almost pure IgG1. More IgG I plus IgG2a, IgG2b and IgG3 are thereafter eluted with acid saline, 90% of the IgG1 which had been eluted with neutral buffer could be re-eluted at the same retarded position with the same buffer. When a gradient from 0 to 3 M sodium thiocyanate was started after the major peak of unbound proteins, all IgG I was eluted before IgG2 and IgG3. These results suggest that IgG1 has a much lower affiniiy for protein A than IgG2 or IgG3 and that normal mouse serum IgG1 can be purified by such a simple procedure.