The Superfamily Of Pyrogenic Toxin Superantigens And The Exfoliative Toxins

The PTSAgs of S. aureus belong to a ''superfamily'' of true exotoxins sharing common phylogenetic relationships, sequence homology, structure, and function.[5] Because they are bivalent molecules that bind two distinct molecules, they are able to stimulate T-lymphocyte proliferation in a non-antigen-specific manner by recognizing T-cell antigen receptor (TCR) Vp and interacting with invariant regions on class II major histocompatibility complex (MHC) products on the surface of antigen-presenting cells (Fig. 1). Thus, by bypassing intracellular processing, they are the most potent activators of T lymphocytes stimulating, at nano- to picogram concentrations, up to 30% of T cells (only 1 in 105-106 T cells is activated upon conventional antigenic peptide presentation to the TCR); hence they are termed ''superantigens.'' This excessive polyclonal activation results in a massive release of proinflammatory cytokines (Fig. 1).[1,2] In addition, staphylococcal PTSAgs have several other important properties contributing to their role in disease. They have mitogenic activity and are able to induce high fevers, stimulate neutrophil recruitment to a site of infection resulting in local inflammation, and enhance host susceptibility to endotoxin shock 100,000- to 1 million-fold.

In contrast to the TSST-1 and SEs, the superantigenic activity of ETs has been debated for years. Whereas the mass of the ETs is similar to that of the staphylococcal PTSAgs, the degree of primary sequence and structural homology is poor.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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