Etiology of organ-specific autoimmunity: Basic research and clinical implications in IBD

Autoimmunity develops in the setting of genetic susceptibility and can be monogenic (eg, autoimmune polyendocrine syndrome type I with Addison's disease, mucocutaneous candidiasis and hypoparathyroidism, which is autosomal recessive with the causative gene on the tip of chromosome 21) or polygenic (usually with important alleles within the major histocompatibility complex [eg, type I diabetes]). In addition to genetic susceptibility, many autoimmune disorders can be classified into etiological categories (oncogenic, drug-induced, diet-induced, infectious or idiopathic). For most autoimmune disorders there are multiple target autoantigens and, for type I diabetes, a combinatorial approach (eg, expression of at least two autoantibodies of insulin, glutamic acid decarboxylase and/or ICA512/IA-2) is the best predictor of diabetes risk. Finally, antigen-specific therapies hold promise for the prevention and therapy of autoimmunity, eg, parenteral or oral therapy with insulin delays or prevents type I diabetes in animal models, and a small pilot trial of parenteral insulin in humans suggests that such therapy may similarly prevent diabetes in humans.