Determination of immunoglobulin class of alloantibodies in sera from hypersensitized renal patients.

26 sera from hypersensitized renal patients were analysed for immunoglobulin class of alloantibodies. To assess the participation of IgM and IgG in alloreactivity, sera were treated with dithiothreitol (DTT) or Staphylococcus aureus protein A (SpA), respectively. Treatment with both DTT and SpA was also performed to test the possible contribution of other immunoglobulin classes. Immunological complexes which may mimic alloreactivity were excluded by polyethylene glycol (PEG) treatment. Immunochemically modified sera were tested against a panel of allogeneic B and T lymphocytes. IgG class alloantibodies reactive with B lymphocytes were found two times more frequently than those reactive with T lymphocytes. In 22% of sera only IgM alloantibodies were detected. No contribution of other immunoglobulin classes of immune complexes was seen. Our results show that DTT and SpA treatment are technically simple and reproducible methods of discriminating between IgG and IgM alloantibodies and can be recommended for routine use in clinical analysis of sera from hypersensitized renal patients awaiting kidney graft.