The Binding of Murine IgM to Staphylococcal A Protein

The binding of Staph A protein to murine immunoglobulins has previously been thought to be restricted to the IgG2 and IgG3 classes. In this study five IgM proteins were assessed for binding, and of these one showed marked Staph A binding. Pepsin digestion of this IgM molecule produced several different sized fragments, and the binding studies with these fragments indicated that the binding site is in the CH2 domain.