The Mechanism of the L‐agglutination of Streptococci by Sera From Patients With Rheumatoid Arthritis

Abstract

e mechanism of the L-agglutination of streptococci by sera from patients with rheumatoid arthritis. Acta path. microbiol. scand. Sect. C, 83: 370-376, 1975. T h e L-agglutination of streptococci group A, strain S.F. 130, type T 1 by sera from patients with rheumatoid arthritis was investigated. T h e IgG fraction of these sera alone could agglutinate the streptococci. Absorption of the sera with the streptococci turned the I,-agglutination test negative. O n addition of pooled human IgG the test was again positive while IgG myeloma protein had no such effect. These findings indicated participation of IgG antibodies to streptococcal antigens and that these antibodies were present also in serum from healthy individuals.If IgG of subclass 1, 2 and 4 was eliminated from the rheumatoid arthritis sera by absorption with Cowan I staphylococci, the L-agglutination could not be restored by addition of pooled human IgG. Together with findings of other authors, this result indicated participation of anti-IgG of IgG class in the I,-agglutination. Furthermore, removal of the broth in which the streptococci were cultured also turned the L-agglutination test with rheumatoid arthritis sera negative, but on replacement with sterile filtered supernatant from gramnegative rods the test again turned positive. T h e interaction of these factors in the L-agglutination---i.e. normally occurring antibodies to streptococcal antigens, anti-IgG of IgG class present in rheumatoid arthritis sera and soluble antigens in the culture supernatant--is discussed.