圓禿疾病之基因分析

Abstract

圓禿落髮（Alopecia areata）是一種無疤痕的落髮疾病，是落髮的最常見原因之一。圓禿具有不可預測的病程和廣泛的臨床表現。不論男女性別都可能會有圓禿落髮發生，一般族群中約有2%的人口比例終其一生會受到圓禿落髮影響。圓禿疾病通常透過臨床上患處皮膚的特徵性『驚嘆號頭髮』來診斷，皮膚切片下的病理表現可在毛囊周邊發現淋巴球細胞浸潤的情形。 根據過去的觀察和研究，圓禿落髮目前被認為是一種複雜、多基因，並且與免疫相關的疾病。過去全基因組關聯分析（Genome-wide association study，GWAS）發現在圓禿落髮中涉及許多免疫和非免疫的相關基因，同時透過免疫螢光染色證實圓禿病灶處CD8+ NKG2D+ T淋巴球參與圓禿落髮的致病機轉。除遺傳因素外，研究發現圓禿疾病的發生和免疫豁免機制的崩損（Immune privilege collapse）息息相關，當頭皮的免疫豁免機制崩損時，體內IFN-r濃度增加，進一步活化頭皮細胞和 CD8+ T淋巴球、CD4+ T淋巴球及Natural killer細胞的作用，而導致落髮。 此次研究主題為研究臺灣圓禿落髮患者是否有異於過往已知圓禿疾病相關的免疫HLA基因，以及圓禿落髮在後天免疫受體庫（germline adaptive immune receptor repertoire，gAIRR）的基因表現。實驗中同時利用探針捕獲次世代定序技術（Capture-based Next-generation Sequencing）分析 DNA中的HLA基因型，以及利用gAIRR Suite探測後天免疫受體庫，包括: T cell receptor和B cell receptor（即Immunoglobulin）在DNA層級上的基因表現。最後分析結果有顯著差異的TCR及IG基因型有TRBJ2-4*01/2-5*01/2-6*01，為保護性基因。為了驗證分析結果，未來需要進一步利用Sanger sequencing及增加受試者人數來確認。

Alopecia area (AA), a nonscarring hair loss disorder, is one of the most common causes of hair loss. AA has an unpredictable course and a wide spectrum of clinical manifestations including patchy AA, alopecia totalis, alopecia universalis, alopecia incognita, ophiasis, sisapho and Marie Antoinette syndrome. AA affects both genders equally and nearly 2% of the general population at some point during their lifetime. AA is usually diagnosed clinically by the characteristic “exclamation mark hair” on the affected skin. Histopathological studies may be required in some cases in which the lesions reveal peribulbar lymphocytic infiltration. According to the recent observations and research, AA is now firmly established as a complex, polygenic, immune-mediated disease. Previous genome-wide association studies (GWAS) have implicated numbers of immune and non-immune loci in the etiology of AA, and the further immunofluorescence stains have showed the critical role of CD8+ NKG2D+ T cells in the pathogenesis of AA. Besides genetic factors, the breakdown of immune privilege in AA also has the great impact on the pathophysiology of AA. In our study, we used the capture-based next-generation sequencing to identify the HLA of alopecia area, and the gAIRR suite to establish the database of the germline adaptive immune receptor repertoires (gAIRR) of alopecia areata. TRBJ2-4*01/ 2-5*01/ 2-6*01 are found to be the significant and protective alleles in this study. In the future, Sanger sequencing and recruiting more subjects will be needed to confirm and replicate the results.