Association of HLA Class I and Class II Genes and Adrenal Steroid 21-Hydroxylase Gene with Subacute (de Quervain’s) and Hashimoto’s Thyroiditis: Evidence for an Altered Negative Feedback in Hashimoto’s Thyroiditis
It is a striking feature of organ-specific autoimmune diseases that they are linked to alleles of class I and class II genes of the MHC gene region ; however, until recently the nature of this association was unclear. The hypothesis was then put forward that the MHC molecules per se play a major role in the immune response. They act as restriction elements when antigen-presenting cell and T cell meet in immune recognition either in a physiological milieu or in an autoimmune state . Direct evidence for this hypothesis was deduced from inappropriate expression of MHC molecules on target tissues of an autoimmune attack, i.e., class II expression on pancreatic beta cells in recent-onset type I diabetes mellitus or class I and class II overexpression on thyroid epithelial cells in Graves’ disease . Presentation of an antigen or an autoantigen is a prerequisite in organ-specific autoimmunity, but also specific recognition by the T-cell receptor supplemented by helper factors is necessary for an immune response . Since organ-specific autoimmune diseases are chronic diseases, it might he speculated that the helper factors (interleukins), which provide a positive feedback, play an important role in the maintenance of chronic inflammation during target organ destruction. Also, negative feedback mechanisms such as T-suppressor circuits may be impaired .
KeywordsCongenital Adrenal Hyperplasia Adrenal Steroid ACTH Stimulation Test Subacute Thyroiditis Histocompatibility Leukocyte Antigen
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