Studies in the Pathogenesis of Systemic Capillary Leak Syndrome

一些证据表明，免疫失调可能是导致SCLS病理生理学改变的原因之一。首先，在大多数SCLS病例中存在一种意义不明的单克隆性伽马病(MGUS)。MGUS是多发性骨髓瘤(MM)的癌前病变，在MM中，克隆性浆细胞群分泌大量可在患者血清中检测到的单克隆性免疫球蛋白(Ig，也称为副蛋白)。同样，在急性SCLS发作期间，循环中CD25+T细胞的数量和皮肤中CD8+淋巴细胞的毛细血管周围浸润也被注意到。最后，几名小细胞淋巴瘤患者在化疗后出现较少的毛细血管渗漏事件。综上所述，这些发现表明，来自失调浆细胞群体的单克隆性副蛋白可能是观察到的病理生理结果的直接或间接来源，可能是通过激活T淋巴细胞。我们正在通过检测单抗Ig在体外血管病理发展中的作用来探索SCLS的分子机制。使用来自SCLS患者的单抗Ig，我们将确定它是否与特定的细胞类型、靶抗原(如果有)结合，以及由此产生的对内皮细胞的影响(直接或间接)。我们还对发病前和发病后SCLS血清的蛋白质组进行了鉴定，以确定是否可以识别急性症状的特定生物标记物。在过去的两年里，我们已经在NIH临床中心评估了23名患者。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病理性增加，但这一假设尚未得到正式检验，部分原因是这种疾病的罕见。我们使用21名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，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。间歇性SCLS血清作用于微血管内皮细胞可引起血管内皮细胞钙粘附素(VE-cadherin)内化，细胞-细胞附加物连接中断，肌动蛋白应激纤维形成，但未见内皮细胞凋亡，而缓解期相同受试者的血清无此作用。急性发作期SCLS患者血清通透性介质血管内皮生长因子(VEGF)和血管生成素2(Ang2)水平明显升高，而无症状期和健康对照组则无明显变化。在一名经历严重SCLS危象的患者中，血管渗漏期开始时，血管内皮生长因子水平急剧升高，随后血管紧张素转换酶2升高较慢。随着外周水肿的消退，两者均恢复到基线水平。我们的结果支持了一种SCLS发病机制的模型，在该模型中，循环通透性介质瞬时激活内皮收缩通路，为这种高度致命的疾病提供潜在的治疗靶点(Ang2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.