Idiotypic and structural analysis of monoclonal human immunoglobulins with anti-streptolysin O activity

The class, subclass and light chain distribution of eight myeloma proteins with anti-streptolysin O activity (ASO) in sera studied by our group and in cases from the literature indicates a predominance of the IgG1 kappa subclass and type of immunoglobulins. Three IgG myeloma proteins (O.I., L.F. and A.S.) were further characterized with respect to idiotypic cross-reaction and variable region subgroup. The anti-idiotypic antibodies (anti-Id) against protein O.I. and against protein L.F. both indicated idiotypic cross-reaction between O.I. and L.F. While in the case of anti-IdL.F. this cross-reaction was in the order of 5% it was much weaker when studied with anti-IdO.I.. The reaction between O.I. and anti-IdO.I. could be inhibited to 95% by the antigen streptolysin O, indicating that the idiotypic determinants are associated with the combining site. N-terminal amino acid sequence analysis showed that all three light chains fall in the V kappa III variable region subgroup. The heavy chains of proteins O.I. and L.F. with idiotypic similarities both have blocked N-termini, indicating the presence of the VHI or VHII subgroup while protein A.S. belongs to the VHIII subgroup.