Superantigens include a class of certain bacterial and viral proteins exhibiting highly potent lymphocyte-transforming (mitogenic) activity toward human and or other mammalian T lymphocytes.[13'14] Unlike conventional antigens, SAgs bind to certain regions of major histocompatibility complex (MHC) class II molecules of antigen-presenting cells (APCs) outside the classical antigen-binding groove. They simultaneously bind under their native form to T lymphocytes bearing certain specific motifs in the variable region of the p chain (Vp) of the T-cell receptor (TcR). The human T-cell repertoire comprises about 24 major types of Vp elements. Each SAg interacts specifically with a characteristic set of Vp motifs. As a consequence, SAgs stimulate at nano- to picogram concentrations up to 30% of T cells, whereas only 1 in 105-106 T cells are activated upon conventional antigenic peptide presentation to TcR in the immune response.
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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.