Epidermolysis bullosa acquisita (EBA) is an autoimmune skin blistering disease characterized by IgG autoantibodies (aAb) against type VII collagen (COL7). The mechanisms controlling the formation of such aAbs and their effector functions in the skin tissue are incompletely understood. Here, we assessed whether the inhibitory IgG Fc receptor, FcγRIIB, controls the development of autoimmune skin blistering disease in an active model of EBA. For this purpose, we immunized congenic EBA-susceptible B6.SJL-H2s (B6.s) and B6.s-Fcgr2b -/- mice with the immunodominant vWFA2 region of COL7. B6.s-Fcgr2b -/- mice developed a strong clinical phenotype with 15 ± 3.3% of affected body surface area at week 4. In contrast, the body surface area in B6.s mice was affected to a maximum of 5% at week 6 with almost no disease signs at week 4. Surprisingly, we already found strong but similar COL7-specific serum IgG1 and IgG2b aAb production at week 2. Further, aAb and C3b deposition in the skin of B6.s and B6.s-Fcgr2b -/- mice increased between weeks 2 and 6 after vWFA2 immunization. Importantly, neutrophil skin infiltration and activation was much stronger in B6s-Fcgr2b -/- than in B6.s mice and already present at week 2. Also, the early aAb response in B6.s-Fcgr2b -/- mice was more diverse than in wt B6.s mice. Reactive oxygen species (ROS) release from infiltrating neutrophils play a crucial role as mediator of skin inflammation in EBA. In line, sera from B6.s and B6.s-Fcgr2b -/- mice induced strong ROS release from bone marrow-neutrophils in vitro. In contrast to the antibody-transfer-induced EBA model, individual targeting of FcγRIII or FcγRIV decreased ROS release to 50%. Combined FcγR blocking abrogated ROS release from BM neutrophils. Also, ROS release induced by COL7-specific serum IgG aAbs was significantly higher using BM neutrophils from B6.s-Fcgr2b -/- than from B6.s mice. Together, our findings identified FcγRIIB as a suppressor of skin inflammation in the active EBA model through inhibition of early epitope spreading, protection from strong early neutrophil infiltration to and activation of neutrophils in the skin and suppression of FcγRIII activation by IgG1 aAbs which drive strong ROS release from neutrophils leading to tissue destruction at the dermal-epidermal junction.

中文翻译：

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Fcγ受体IIB在表皮松解大疱性活动模型中控制皮肤炎症。

大疱表皮松解症（EBA）是一种自身免疫性皮肤水疱性疾病，其特征在于针对VII型胶原（COL7）的IgG自身抗体（aAb）。在皮肤组织中控制此类aAb的形成及其效应子功能的机制尚不完全清楚。在这里，我们评估了抑制性IgG Fc受体FcγRIIB在EBA活跃模型中是否控制了自身免疫性皮肤水疱病的发展。为此，我们用COL7的免疫优势vWFA2区域免疫了易感染EBA的同基因B6.SJL-H2s（B6.s）和B6.s-Fcgr2b-/-小鼠。B6.s-Fcgr2b-/-小鼠表现出很强的临床表型，在第4周的患病表面积为15±3.3％。相比之下，B6.s小鼠的体表面积在第7周受累最大为5％。 6周4几乎没有疾病迹象。我们已经在第2周发现强烈但相似的COL7特异性血清IgG1和IgG2b aAb产生。此外，在vWFA2后的第2周和第6周之间，B6.s和B6.s-Fcgr2b-/-小鼠皮肤中的aAb和C3b沉积增加了。免疫。重要的是，B6s-Fcgr2b-/-的中性粒细胞皮肤浸润和激活比B6.s小鼠强得多，并且已经存在于第2周。而且，B6.s-Fcgr2b-/-小鼠的早期aAb反应比在wt B6.s小鼠中。浸润性中性粒细胞释放的活性氧（ROS）在EBA中起皮肤炎症介质的作用。一致地，来自B6.s和B6.s-Fcgr2b-/-小鼠的血清在体外诱导从骨髓-中性粒细胞中强烈的ROS释放。与抗体转移诱导的EBA模型相反，对FcγRIII或FcγRIV的单独靶向将ROS释放降低至50％。联合的FcγR阻断可消除BM中性粒细胞的ROS释放。同样，使用B6.s-Fcgr2b-/-的BM中性粒细胞，COL7特异性血清IgG aAbs诱导的ROS释放明显高于B6.s小鼠。总之，我们的发现通过抑制早期表位扩散，防止强烈的早期嗜中性粒细胞浸润和中性粒细胞活化以及抑制IgG1 aAb抑制FcγRIII的活化，从而在活跃的EBA模型中将FcγRIIB抑制为皮肤炎症，并驱动ROS强烈从嗜中性粒细胞释放导致真皮-表皮交界处的组织破坏。