Lesional infiltration of eosnophils is a distinguishing histopathologic characteristic for bullous pemphigoid (BP). However, the actual contribution of eosnophils to the   pathogenesis of BP is largely unknown. Semaphorin 4D (Sema4D) is constitutively expressed on granulocytes and plays important roles in B cell regulation, but its implication in BP remains obscure. Here, we descried that eosnophils, marked as CD15+ granulocytes in patients with BP presented much lower expression of membrane-bound Sema4D (mSema4D) in both peripheral blood and blister fluid. Consistently, the levels of both lesional and circulating sSema4D were significantly elevated and well correlated with anti-BP180 antibody titer. Moreover, healthy-derived CD15+ granulocytes activated by PMA started spontaneous shedding of mSema4D and generating 120kDa-sized sSema4D into cell supernatants, which can be specifically blocked by ADAM10 inhibitor. Conformably, membrane-bound ADAM10 (mADAM10) was abundantly expressed on activated CD15+ granulocytes despite its absence before activation. Meanwhile, we found that soluble ADAM10 (sADAM10) treatment can directly cause mSema4D cleavage from CD15+ granulocytes. In line with in vitro findings, sADAM10 displayed a prominently high level in the blister fluid and mADMA10 was extensively expressed on CD15+granulocytes from BP patients but nearly absent on those from healthy individuals. Furthermore, in patient-derived PBMCs, by promoting the differentiation of B cell into plasmablasts, sSema4D specifically boosted anti-BP180 antibody production in a time- and dose- dependent manners, which was attributed to CD72-mediated activation of Akt/NF-κB p-65/Erk cascades in B cells. Our findings revealed a novel role of eosnophils in ADAM10-dependent Sema4D shedding that ultimately caused augmented pathogenic antibody and aggravated autoimmune responds, thus providing a new insight into the BP pathogenesis.

ADAM10-induced Cleavage of Semaphorin 4D from Eosnophils Contributes to Antibody Production in Bullous Pemphigoid