Mouse IgG1 heterogeneity: variable binding of monoclonal IgG1 antibodies to protein A-sepharose

Binding strength to protein A discriminates three definitive types of mouse monoclonal IgG1. Each of these types of IgG1 elutes from protein A-Sepharose as a coherent peak representing the great majority of IgG1 protein. One type of IgG1 is not present to any significant extent in polyclonal mouse IgG preparations, and to our knowledge has not been reported previously. This type of IgG1 does not bind firmly to protein A at pH 8.0, but is retarded sufficiently that it can be purified by protein A-Sepharose chromatography in high yields.