Binding of Canine IgM and IgG to Protein A of Staphylococcus aureus: A Simple Method for the Isolation of Canine Immunoglobulins from Serum and the Lymphocyte Surface

SUMMARY The binding of normal canine serum IgG and IgM to staphylococcal protein A is described. Virtually all (> 99%) of IgG and up to 90% of IgM could be removed from canine serum, utilizing this phenomenon. The nature of the bound material was confirmed by immunodiffusion in agar, radioimmunoassay, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Attempts to elute differentially IgG and IgM from protein A-Sepharose columns, using gradients of pH or the chaotropic agent sodium thiocyanate, were unsuccessful. This phenomenon provides a basis for the isolation of canine IgM from serum. Lymphocyte surface IgM, studied by lactoperoxidase-catalyzed membrane radioiodination and solubilization in nonionic detergent, also showed the property of binding to staphylococcal protein A.