Inhibition of complement fixation by human serum, II. The activity of a -1M globulin and rheumatoid factor in complement fixation reactions

Heimer, Ralph; Levin, F.M.; Kahn, M.F.

Jour Immunol 91(6): 866-872


Accession: 024867261

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Heated rheumatoid arthritis and normal sera, rheumatoid factor and "inhibitor (Ag-Ab)", a gamma-1M- globulin isolated from rheumatoid sera, were tested by kinetic and static assays for ability to inhibit complement fixation reactions. Rheumatoid arthritis and normal serum delayed immune hemolysis of sensitized cells. Preabsorption of sera with heated gamma-globulin did not affect the inhibitory activity. "Inhibitor (Ag-Ab) " delayed immune hemolysis and inhibited complement fixation by antigen-antibody complexes. Complement fixation reactions by latex particles coated with human gamma-globulin remained unaffected. Rheumatoid factor did not interfere with the lysis of sensitized cells and was also inactive in complement fixation reactions involving antigen-antibody complexes. However, it inhibited complement fixation by latex particles coated with gamma-globulin. Guinea pig serum decreased the latex fixation titer of rheumatoid arthritis sera, suggesting some competition between rheumatoid factor and complement for sites of attachment on gamma-globulin.