The immunological specificity of type II Pneumococcus and its separation into partial specificities. II.

Quantitative data are given on the cross reactions in Type II antipneumococcal horse sera of plant gums and hemicelluloses containing multiple terminal groupings of glucuronic acid and/or 4-O-methylglucuronic acid. Great variability is shown both in the reactivities of the polysaccharides and in the antibodies in the sera of different animals immunized with the same antigen. The 4-O-methyl substituent on the glucuronic acid residues in a gum often appears to diminish cross-precipitation with antibodies to S II.