Binding of enzyme--IgG complexes in human serum to Protein-A Sepharose CL-4B

We describe a simple method for detecting enzyme--immunoglobulin G (IgG) complexes in human serum. Protein-A Sepharose CL-4B binds IgG and therefore also the enzyme--IgG complexes, which can then be separated easily from the serum by centrifugation. We demonstrate this separation in two patients, one with a complex of IgG and creatine kinase (EC 2.7.3.2) BB isoenzyme, the other with an IgG--alkaline phosphatase (EC 3.1.3.1) complex. Both patients had unexplainably high activities of the respective enzymes in their serum. The method we propose should be a useful, simple, routine method of detection in cases where IgG--enzyme complexes are suspected.