Biomedical subjects
Publications and source records attributed to I M Lyampert.
Immunization of animals with a polypeptide fragment of the streptococcal group A M protein (pep M) conjugated with a synthetic copolymer caused a significant increase in the titres of bactericidal type-specific antibodies. In some cases bactericidal antibodies to streptococci of other types were also induced.
Normal human and rabbit sera, and the IgG isolated from them, have been shown by immunofluorescence to react with bovine and human heart valve fibroblasts. Analogous results were obtained with sera of children under the age of 2. Positive reactions were observed also with fibroblasts, chondrocytes and osteocytes of human fetal joint tissues. The reactions are mostly due to monomeric immunoglobulins, since soluble immune complexes give much weaker reactions with the fibroblasts. The reactions are apparently dependent on the presence of Fc receptors on these cells. This conclusion is confirmed by positive reactions with IgG Fc fragments, with pure antibodies to ovalbumin and with human monoclonal IgG. The monoclonal IgG1 possesses the strongest ability to bind with fibroblast Fc receptors. No Fc-IgG receptors have been revealed on the fibroblasts and other structures of the interstitial connective tissue of human and bovine myocardium.
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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.
Two common (non-type-specific) antigens in HCl extracts prepared from group A streptococcal cultures of different types were analyzed by immunodiffusion methods. These antigens are sensitive to trypsin and are apparently related to the cell wall proteins. The common antigens tested belong to a category of nonprotective non-type-specific antigens. The presence of common antigens in the HCl extracts should be taken into consideration when M-proteins are determined. The detection of one of the common antigens may be used as a virulence index, since this antigen is characteristic of the group A streptococcal cultures with enhanced virulence.
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.
Immunofluorescence studies show that thymus epithelial cells react with antibodies to group A streptococcal polysaccharide.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.