Studies in the Pathogenesis of Systemic Capillary Leak Syndrome

一些证据表明，免疫失调可能有助于在SCLS中观察到的病理生理学结果。首先，意义不明的单克隆丙种球蛋白病（MGUS）存在于大多数SCLS病例中。 MGUS是多发性骨髓瘤（MM）的癌前前病变，其中克隆浆细胞群分泌大量可在患者血清中检测到的单克隆免疫球蛋白（IG，也称为副蛋白）。 同样，在急性SCLS发作期间，已经注意到皮肤中循环CD 25 + T细胞的数量增加和CD 8+淋巴细胞的毛细血管周围浸润。最后，有几名SCLS患者在MGUS演变为坦率的骨髓瘤或浆细胞白血病后经历了较少的毛细血管渗漏发作化疗的造血系统疾病。 综合考虑，这些结果表明，来自调节异常的浆细胞群的单克隆副蛋白可能是观察到的病理生理学结果的直接或间接来源，可能通过激活T淋巴细胞。我们正在通过检测单克隆IG在体外血管病理学发展中的作用来探索SCLS的分子机制。使用SCLS患者的单克隆IG，我们将确定其是否与特定细胞类型、靶抗原（如果有）结合，以及对内皮细胞的影响（直接或间接）。我们还对SCLS血清蛋白质组进行了表征，包括发作前和发作后，以确定是否可以识别急性症状的特定生物标志物。在过去的2年里，我们已经根据该方案对23例NIH临床中心的患者进行了评估。我们现在是SCLS研究的主要全球转诊中心。 虽然这种疾病的命名意味着血管通透性的致病性增加，但这一假设尚未得到正式验证，部分原因是由于这种疾病的罕见性。我们使用21例患者的血液样本进行了机制研究，这是迄今为止最大的SCLS病例系列，并发现了循环血管生成因子对SCLS临床症状的致病作用的证据。将SCLS血清应用于微血管内皮细胞引起血管内皮钙粘蛋白（VE-钙粘蛋白）内化，破坏细胞-细胞粘附连接和肌动蛋白应力纤维形成，而没有内皮细胞凋亡，而缓解期间获得的相同受试者的血清没有这样的影响。在急性发作期间，SCLS血清中渗透介质血管内皮生长因子（VEGF）和血管生成素2（Ang 2）的水平显著升高，但在无症状期或健康对照受试者中则无此现象。在经历严重SCLS危象的单个患者中，VEGF水平在血管渗漏阶段开始时飙升，随后Ang 2缓慢上升。随着外周水肿消退，两者均恢复至基线水平。我们的研究结果支持SCLS发病机制的模型，其中循环渗透性介质瞬时激活内皮收缩通路，为这种高致死性疾病提供潜在的治疗靶点（Ang 2和VEGF）。

Several lines of evidence suggest that immune dysregulation may contribute to the pathophysiologic findings seen in SCLS. First, a monoclonal gammopathy of unknown significance (MGUS) is present in a majority of SCLS cases. MGUS is a premalignant precursor to multiple myeloma (MM), in which a clonal plasma cell population secretes large amounts of monoclonal immunoglobulin (Ig, also referred to as a paraprotein) detectable in patient sera. Likewise, increased numbers of circulating CD25+ T cells and peri-capillary infiltration of CD8+ lymphocytes in skin have been noted during acute SCLS attacks. Finally, several patients with SCLS in whom MGUS evolved into frank myeloma or plasma cell leukemia experienced fewer capillary leak episodes after chemotherapy for the hematopoietic disorder. Considered together, these findings suggest that the monoclonal paraprotein from the dysregulated plasma cell population may be the direct or indirect source of the pathophysiologic findings observed, possibly through activation of T lymphocytes. We are exploring the molecular mechanisms of SCLS by examining the function of the monoclonal Ig in the development of vascular pathology in vitro. Using monoclonal Ig from SCLS patients, we will determine whether it binds to a specific cell type, target antigen (if any), and resulting effect (direct or indirect) on endothelial cells. We are also characterizing the proteome of SCLS serum, both pre- and post-attack, to determine whether specific biomarkers of acute symptoms can be identified. We have now evaluated 23 patients to the NIH clinical center under this protocol in the last 2 years. We are now the primary worldwide referral center for research on SCLS. Although the nomenclature of this disorder implies a pathogenic increase in vascular permeability, this hypothesis has not been formally tested, in part due to the rarity of the condition. We performed mechanistic studies using blood samples from 21 patients, the largest SCLS case series to date and found evidence for the pathogenic contribution of circulating angiogenic factors to the clinical symptoms of SCLS. Application of episodic SCLS sera to microvascular endothelial cells caused vascular endothelial cadherin (VE-cadherin) internalization, disruption of cell-cell addherens junctions, and actin stress fiber formation without endothelial apoptosis whereas the sera from the same subjects obtained during remission had no such effects. Levels of permeability mediators vascular endothelial growth factor (VEGF) and Angiopoietin 2 (Ang2) were significantly elevated in SCLS sera during acute episodes but not in asymptomatic periods or healthy control subjects. In a single patient experiencing a severe SCLS crisis, VEGF levels spiked at the beginning of the vascular leak phase followed by a slower rise in Ang2. Both returned to baseline as peripheral edema resolved. Our results support a model of SCLS pathogenesis in which circulating permeability mediators transiently activate endothelial retraction pathways, providing potential therapeutic targets (Ang2 and VEGF) for this highly lethal disorder.