Detection of mycoplasmal antigens in immune complexes from rheumatoid arthritis synovial fluids

This study was directed towards the detection of suspected antigenic microbial fragments in the immune complex (IC) fraction from chronic inflammatory disorders of the delayed type allergy. Mycoplasmas as the microbial prototype and joint fluids from the rheumatoid host were investigated. Protein-A affinity chromatography was used to isolate the immunoglobulin complex (IgG-IC) in six synovial fluids obtained from rheumatoid arthritis patients. The IgG-IC was digested with pepsin to further purify and obtain F(ab)2 complexes with greater specificity. The F(ab)2 complexes were dissociated and electrophoresed by SDS-PAGE and analyzed by immunoblotting using affinity purified rabbit antisera to six reference strains of human mycoplasmas. The presence of trace amount of mycoplasma antigens in the immune complex fractions was indicated by specific banding with antisera to M. pneumoniae, M. arthritidis, M. hominis, M. fermantans, and M. salivarium in one or more of the six synovial fluid fractions. The ELISA and immunoblot assays of seroconversion in rabbits immunized with the synovial fluid fractions also indicated the presence of mycoplasmal antigens.