[Group A streptococcal polysaccharide--an inhibitor of the functional activity of T-suppressors induced by Con A in a culture of mononuclear cells of human peripheral blood].

It was found that group A streptococcal polysaccharide (A-PS) had no mitogenic effect on the intact human blood mononuclear cells' culture (MNC) and on its proliferation stimulated with ConA. Using a double staining technique for simultaneously determining cell surface phenotype and degree of cell activation by it's ability to include the tetrazolium dye MTT (3-[4,5-dimethylthiazol-2-yl] -2,5-diphenyl tetrazolium bromide) it was established that A-PS decreased the percent of activated (MTT+) cells in the subpopulation of CD8+ and increased the percent of MTT+ cells among CD4+ lymphocytes in the intact MNC. In the MNC stimulated with ConA A-PS caused only one of these effects: it decreased the percent of MTT+ cells in the subpopulation of CD8+ lymphocytes. The correlation was established between the results obtained with MTT-technique and cell transfer test, because the MNC preincubated with ConA and A-PS lost the ability to suppresses MNC proliferation stimulated with PHA. The data obtained supported the assumption that A-PS as a carrier of determinants common with thymus epidermal antigens (factors) may act as it's functional analogue and thus promote the development of autoimmune process during the rheumatic fever.