Antigenic Action of the Specific Polysaccharide of Pneumococcus Type I in Man

Abstract

Francis and Tillett 1 demonstrated that following the intradermal injection of minute amounts of the type-specific polysaccharide of Type I, II or III Pneumococcus in humans, there developed in the serum of these individuals homologous type-specific agglutinins. In addition, the serum of individuals so treated was found to possess the capacity of conferring passive protection upon mice against infection with pneumococci of homologous type. These results were confirmed by Finland and Sutliff. 2

Recently, it has been shown that the specific polysaccharide of Type I Pneumococcus exists as an acetyl polysaccharide. 3 The acetyl compound is capable of completely absorbing the type-specific antibodies from an homologous immune serum and of inducing type-specific active immunity in mice. The acetyl polysaccharide is readily converted into its deacetylated derivative by treatment with dilute alkali. The chemical and immunological properties of the deacetylated polysaccharide are identical with those of the soluble specific substance in the form in which it was originally isolated⁴; it is non-antigenic in mice and only partially absorbs the type-specific antibodies from Type I anti-pneumococcus serum.

The recognition of the specific polysaccharide in acetyl form raised the question as to whether the antigenicity of the pneumococcus carbohydrates previously observed in humans had been due to the deacetylated product or to contaminations of that material with the acetyl polysaccharide. Consequently, 2 groups of normal humans, each 7 in number, were given intradermal injections of the acetyl polysaccharide and the deacetylated polysaccharide of Type I Pneumococcus, respectively. The deacetylated product was prepared by Dr. W. F. Goebel from the same lot of acetyl polysaccharide used in the experiment. An injection of 0.01 mg. in 0.1 cc. of physiological saline was made intradermally in each individual at weekly intervals for 3 weeks. Serum was obtained from each person before the first injection and again one week after the third injection. These sera were then tested for the presence of type-specific agglutinins, precipitins and mouse-protective antibodies.