| Systemic autoimmune diseases are a set of diseases in many of which etiology is unknown and involves diverse pathogenesis, many kinds of autoantibodies, disturbances in quantity and/or function of lymphocytes, resulting in breakdown of immunoregulation of cytokine network, leading to bizarre diffuse and/or local immune disorders. Because of unknown etiology, these diseases are difficult to treat. In recent years, a population of T cells ,the TCR γ δ subsets, was identified. The majority of γ/ δ T cells are CD3+CD4-CD8- so-called double-negative T cells, which represents a minor portion(0.5~10%) of peripheral CD3+ T cell population in normal human beings. γ /δ T cell shares many characteristics with α/β T cell, for example, in the immune system they can be cytotoxic, producing an array of cytokines, and helping B cells to differentiate to Ig-secreting cell. Nevertheless, γ /δ T cells remain a special subset of T cells, sometimes possessing distinctly different characteristics from TCRα/β T cells. Firstly, the majority of TCR γ /δ cells have a restricted tissue distribution. TCR γ /δ cells predominate in the epithelial linings of the intestine, lung, skin, and reproductive tract, often times the first front line of host defense mechanism. Secondly, TCR γ /δ cells have a more limited TCR repertoire than TCR α/β cells. Thirdly, TCR γ δ cells do not appear to recognize the same types of antigens as TCR αβ cells do, moreover, they are usually MHC-independent in antigens recognition. Aside from polypeptide, they can recognize phospholigand, ethyl antigens and heat shock...
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