Superantigens of Group A Streptococci (Streptococcus pyogenes)
The erythrogenic (pyrogenic) toxins ETA and ETC have been characterized as superantigens, which bind as native molecules to MHC class II molecules of antigen processing cells and to T-cell receptors possessing specific Vß-chains. Linking these two receptors results in a high release of cytokines. ETB was recognized as the precursor of the streptococcal proteinase. Mitogenic activity detected in preparations of ETB by some authors was found to be a contamination, recently isolated and described as toxin AX (1). It is accompanied by a second component BX, which differs only by the lack of the amino terminal arginine. The immunological reactions of both proteins are identical, but the mitogenic activity of BX is failed higher than that of AX.
KeywordsHaCat Cell Raji Cell Mitogenic Activity Human Cell Type Streptococcal Toxic Shock Syndrome
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