Immunodiffusion method for identification of group A streptococci.

The development of a method suitable for identification of group A streptococci by microprecipitation in gels is described. The method is based on preparation of specific sera containing high antibody levels agains the antigenic determinant characteristic of group A streptococcal polysaccharide. In a comparative study with a counterimmunoelectrophoresis method, the proposed test proved to be specific, easily read, and less complicated. Results were obtained in 2 h.

A cross-reactive antigen of thymus and skin epithelial cells common with the polysaccharide of group A streptococci.

Investigation of antibodies to the specific determinant of streptococcal group A polysaccharide in indirect immunofluorescence experiments has revealed the existence of a cross-reactive antigen in the epithelial cells of the thymus and skin. This CR antigen is contained by the epithelial cells of man and animals of different species. It has been demonstrated in all the individuals studied including animals producing antibodies to the polysaccharide of Group A streptococci. The principal cause of autoimmune thymitis characteristic of rheumatic fever and other autoimmune processes is probably damage done to the thymus by autoantibodies resulting from immunization with microbial cross-reactive antigens shared by the thymus. Reaction of the autoantibodies with thymic antigens may affect the immunosuppressive function of the thymus and the maturation process of suppressor T cells. These events probably constitute the basic stage in the development of an autoimmune process.

Reaction of thymus epithelial cells with antibodies to group A streptococcal polysaccharide.

Immunofluorescence studies show that thymus epithelial cells react with antibodies to group A streptococcal polysaccharide.