title: Interaction of S-sulfonated human IgG with human complement and its components.
abstract: S-sulfonated human IgG (S-sIgG) was prepared by treating IgG with sodium sulfite and sodium tetrathionate. The treatment resulted in the selective cleavage of interchain disulfide bonds of the IgG to give S-sulfonate groups. Complement fixing activities of aggregated S-sIgG and the immune complex formed with the S-sIgG antibody were very weak. S-sIgG at a high dose reduced the activity of the first complement component (C1) in normal human serum without any reduction of other complement components activites, but S-alkylated IgG at the same dose did not. Loss of C1 activity was not caused by either S-sulfonated myeloma proteins (IgA and IgE) or urea-treated S-sIgG, in which both inter- and intra-chain disulfide bonds were cleaved. These results suggest that the selective reduction of C1 by S-sIgG is due to a conformational change of the immunoglobulin.
mesh_terms: D003168:Complement Fixation Tests; D003165:Complement System Proteins; D004220:Disulfides; D006461:Hemolysis; D006801:Humans; D007074:Immunoglobulin G; D010434:Pepsin A; D013451:Sulfonic Acids
chemical_list: D004220:Disulfides; D007074:Immunoglobulin G; D013451:Sulfonic Acids; D003165:Complement System Proteins; D010434:Pepsin A