Alopecia areata is a condition that affects hair follicles and leads to hair loss ranging from small well-defined patches to complete loss of all body hair. Despite its high incidence, the pathobiology is not fully understood, and no single concept could be universally accepted. Alopecia areata is mostly considered to be an autoimmune disease, in which the collapse of hair follicle immune privilege plays a key role. Higher incidence rate in the female population and increased overall risk of other autoimmune disorders militate in favor of autoimmune hypothesis. Antibodies against multiple components of hair follicles almost exclusively attack in anagen phase, where melanogenesis takes place. It suggests involvement of melanogenesis-associated autoantigens as a target epitope. Some investigators believed that alopecia areata is not a truly autoimmune disease but is only ‘consistent with’ autoimmune mechanisms. High frequency of a positive family history up to 42% may reflects the contribution of heredity factors. In addition, no specific target autoantigen has been identified so far, and autoantibodies to hair follicle-associated antigens are detectable in normal individuals.

中文翻译：

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斑秃的免疫学

斑秃是一种影响毛囊并导致脱发的疾病，从定义明确的小斑块到全身毛发完全消失。尽管发病率很高，但病理生物学尚未得到充分理解，并且没有一个概念可以被普遍接受。斑秃通常被认为是一种自身免疫性疾病，其中毛囊免疫特权的下降起着关键作用。女性人群中较高的发病率和其他自身免疫性疾病的总体风险增加，有利于自身免疫假说。针对毛囊多个组成部分的抗体几乎完全在生长期发生于黑色素生成的阶段发作。它提示黑色素生成相关的自身抗原作为靶抗原决定簇。一些研究者认为斑秃不是真正的自身免疫性疾病，而仅与自身免疫机制“保持一致”。高达42％的家族史阳性的高频率可能反映了遗传因素的贡献。另外，到目前为止，尚未鉴定出特异性的靶自身抗原，并且在正常个体中可检测到与毛囊相关抗原的自身抗体。