The Role of Monocyte-derived Cells and the molecular Mechanisms of their Recruitment in the Pathogenesis of Pemphigoid Diseases

效应细胞向皮肤中的募集是PD中引发和加剧皮肤炎症的致病关键过程。从血管腔到真皮-表皮交界处（DEJ）的效应细胞募集的时空动力学以及编排这种募集的分子线索知之甚少。在第一FP中，我们已经着手通过活体多光子显微镜（IMM）绘制新出现的PD皮肤病变中不同效应细胞群（包括PMN和单核细胞）招募的时空动态。我们还开始揭示负责早期效应细胞募集的分子线索，本文主要关注白三烯B4（LTB 4）及其受体BLT 1。我们已经发现，在DEJ处自身抗体沉积后几个小时，皮肤中产生了大量的LTB 4，并且对于启动PMN和单核细胞向皮肤中的募集以及因此沉淀皮肤病变是必不可少的。我们还破译了补体片段C5 a及其受体C5 aR 1作用于LTB 4的上游，并推测启动其释放。这些发现已经促使了与制药公司的合作。因此，我们即将测试新型LTB 4和C5抑制剂在BP患者中的疗效。 绘制效应细胞募集的动力学，我们已经解开，出乎意料的是，直到抗体沉积后第3天，PMN才被大量募集到皮肤中。相比之下，单核细胞被招募到皮肤中，并在抗体沉积后几乎立即被引导到DEJ，这表明单核细胞可能协调随后大量的中性粒细胞流入皮肤。此外，我们已经发现的证据表明，在皮肤炎症的后期阶段，单核细胞可能会与中性粒细胞在执行真皮表皮裂缝的形成。总的来说，我们的研究结果强调单核细胞是PD皮肤炎症的潜在、先前被监督的主要贡献者。因此，在第二次FP中，我们将系统地研究单核细胞在PD中的作用，重点是它们作为PMN募集促进者的假定作用。我们还将阐明介导单核细胞募集到皮肤中的分子机制。我们假设这些分子机制依赖于C5 a/C5 aR 1-LTB 4/BLT 1轴，从而为LTB 4/BLT 1或C5 a/C5 aR 1抑制剂在PD中的疗效提供了进一步的证据。重要的是，我们还将分析BP患者的单核细胞群体及其动态，以将我们的发现转化为人类情况，并评估单核细胞作为潜在药物靶点和生物标志物的可能性。

The recruitment of effector cells into the skin is the pathogenic key process initiating and fueling skin inflammation in PDs. The spatiotemporal dynamics of effector cell recruitment from the blood vessel lumen to the dermal-epidermal junction (DEJ) as well as the molecular cues choreographing this recruitment are only poorly understood. In the 1st FP, we have set out to chart the spatiotemporal dynamics of the recruitment of different effect cell populations, including PMNs and monocytes, in emerging PD skin lesions by intravital multiphoton microscopy (IMM). We have also set out to unfold the molecular cues responsible for early effect cell recruitment, herein primarily focusing on leukotriene B4 (LTB4) and its receptor BLT1. We have uncovered that already few hours after the deposition of autoantibodies at the DEJ, significant amounts of LTB4 are generated in the skin and are indispensable to initiate the recruitment of both PMNs and monocytes into the skin and, consequently, to precipitate skin lesions. We have also deciphered that the complement fragment C5a and its receptor C5aR1 act upstream of LTB4 and presumably initiate its release. These findings have already instigated collaborations with pharmaceuticals companies. As a result, we are about to test the efficacy of novel LTB4 and C5 inhibitors in BP patients. Charting the kinetics of effector cell recruitment, we have unraveled that, unexpectedly, PMNs are not recruited in significant numbers into the skin until day 3 after antibody deposition. In contrast, monocytes are recruited into the skin and guided to the DEJ almost immediately upon antibody deposition, suggesting that monocytes may orchestrate the subsequent massive influx of PMNs into the skin. In addition, we have found evidence that in later stages of skin inflammation monocytes may act in concert with PMNs in executing dermal-epidermal cleft formation. Collectively, our findings highlight monocytes as potential, previously overseen, major contributors to PD skin inflammation. In the 2nd FP, we will therefore systematically investigate the role of monocytes in PD, focusing on their putative role as facilitators of PMN recruitment. We will also elucidate the molecular mechanisms mediating the recruitment of monocytes into the skin. We hypothesize that these molecular mechanisms depend on the C5a/C5aR1-LTB4/BLT1 axis, thus providing further evidence for the efficacy of LTB4/BLT1 or C5a/C5aR1 inhibitors in PDs. Importantly, we will also profile monocyte populations and their dynamics in BP patients to translate our findings into the human situation and evaluate monocytes as potential drug targets and biomarkers