INTERACTION OF THE FC PART OF IGG WITH LANCEFIELD EXTRACTS OF HEMOLYTIC STREPTOCOCCI - STRAIN SPECIFICITY AND ACTIVITY

Abstract

Lancefield extracts of 19 types of group A streptococci and 1 group C and 1 group G strain were examined for agglutination of human red cells coated with various anti-Rh antibodies. Fourteen extracts agglutinated 1 or more of the coated cell samples, while 5 did not. The agglutination was inhibited by Fc but not by Fab fragments of human Ig[immunoglobulin]G. After mouse passages, 3 of the non-agglutinating strains acquired agglutinating capacity. At least 3 different reactivities were distinguished by the action of the extracts on IgG1 and IgG3 coated cells, respectively. Of the streptococcal extracts agglutinating the same anti-Rh coated cells, 2 could be further differentiated in hemagglutination inhibition (HAI) experiments using purified IgG3 myeloma proteins. Five selected agglutinating systems were inhibited by purified myeloma proteins of the IgG1, IgG2 and IgG4 subclasses. IgG3 proteins inhibited only 2 of the 5 HAI systems.