Isolation and characterization of the epidermolysis bullosa acquisita antigei

获得性大疱性表皮松解症是一种自身免疫性水疱病，临床特征为轻度外伤性大疱性大疱病。组织学检查显示大疱性病变发生在真皮下区域。本病患者有抗基底膜带的循环自身抗体。与这种自身抗体反应的自身抗原是III型胶原，它是锚定纤维的主要成分。为了分离编码该自身抗原的c DNA并对其进行鉴定，我们首先筛选了与人角质形成细胞m RNA相对应的c DNA文库。用与VII型胶原特异结合的单抗克隆了插入-1Kb的c DNA。Northern杂交显示-9.5Kb的单一条带。为此，我们于1993年对文库进行了重新筛选，获得了扩增克隆。合成的cDNA相互重叠，几乎覆盖了III型胶原的N端非冷却域。核苷酸序列和推导的氨基酸序列表明，该分子与纤维连接蛋白的11L型重复序列具有同源性，2)具有内部重复单位，3)重复单位之间的同源性类似于纤维连接蛋白III型重复序列。这些结果有力地提示，III型胶原的N端非胶原区具有与纤连蛋白相似的结构，并可能具有与该大分子类似的功能，如与其他蛋白质的结合。

Epidermolysis bullosa acquisita is an autoimmune blistering disease, clinically characterized with mild trauma inducible bulla. Histological examination revealed that bulla develops in the subepidermal region. Patients with this disease have circulating autoantibodies against basemen membrane zone. The autoantigen reactive to this autoantibodies is type VII collagen which is a major component of an anchoring fibril. To isolate cDNA which code this autoantigen and to characterize this autoantigen, we first started to screening the cDNA library which corresponds io human keratinocyte mRNA.A cDNA with an insert of -1Kb was isolated with monoclonal antibody that specifically bind to type VII collagen. Northern blot revealed -9.5Kb single band. Therefor in 1993, we re-screened the cDNA library to obtain the extended clones. The resultant cDNAs, overlapping to each other, cover almost all the N-terminal non-coolagenous domain of type VII collagen. The nucleotide sequence and the deduced amino acid sequence revealed that 1 ) this molecules has a homology to type lll repeat of fibronectin, 2) it has internal repeating unit, and 3) homoiogy between the repetitive unit is similar to those of fibronectin type III repeat. These reuslt strongly suggest that the N-terminal non-collagenous domain of type VII collagen has similar structure to fibrionectin and that it may possese similar function to this macromolecule such as bindiong to other proteins.