Critical Role of Basophils in the Enhancement of the Innate Immune Response during Sepsis

项目总结 每年约有850,000例新的败血症病例，死亡率从240,000- 375,000。先天免疫反应受损可通过损害 病人抵抗感染的能力。然而，增强先天免疫的细胞和介质 对脓毒症的反应仍不清楚。嗜碱性粒细胞占外周血白细胞的比例不到1%，这 使它们成为已知的最稀有的粒细胞。嗜碱性细胞在进化上在许多动物物种中是保守的， 这表明嗜碱性细胞的作用是有益的，而不是有害的。然而，目前尚不清楚嗜碱性粒细胞是否 在宿主对细菌的防御中发挥任何作用，从而潜在地防止败血症的发展。我们的 初步研究表明，嗜碱性粒细胞是最早积累的细胞之一，从而支持这种作用。 在感染早期的感染部位，并可以提高存活率和细菌清除 盲肠结扎穿孔(CLP)所致脓毒症的多菌模型。我们认为我们在 小鼠的系统可能对人类是可翻译的，因为我们观察到创伤患者表现出增加 医院感染局限于局部组织时循环中的嗜碱性粒细胞数量(早期 感染阶段)，而嗜碱性粒细胞数量减少或保持不变，当患者发生 全身感染(菌血症)，因此发展成败血症的风险很高。基于这些研究， 我们推测嗜碱性粒细胞通过增强先天免疫反应在脓毒症中起到保护作用。 抗感染。因此，我们提出了一项研究计划，旨在调查嗜碱性粒细胞的贡献 对细菌的先天免疫反应。在目标1中，我们将确定与嗜碱性粒细胞有关的机制 在感染过程中被激活。我们将使用遗传学方法来研究嗜碱性细胞刺激 通过TLR和MyD88途径，需要诱导嗜碱性细胞活化和提供保护 感染；我们将检查上皮细胞衍生的细胞因子，胸腺基质淋巴生成素 (TSLP)，可以增强嗜碱性粒细胞对感染的反应能力。在目标2中，我们将定义 嗜碱性细胞保护细菌免受感染的机制。具体地说，我们将调查 微血管系统中嗜碱性粒细胞、内皮细胞和循环白细胞之间的相互作用 将使用嗜碱性粒细胞特异性肿瘤坏死因子缺乏的小鼠来研究CLP期间的这些相互作用。在《目标3》中，我们将 确定嗜碱性粒细胞在人类感染和败血症中的相关性。具体地说，我们将使用质量细胞术 (CyTOF)评估从发生医院感染的患者采集的样本中的嗜碱性粒细胞免疫功能 感染，主要是肺炎，我们将确定这些免疫功能是否与临床相关 结果。我们认为，提出的研究将扩大我们对脓毒症生理病理学的认识。 具体地说，我们的研究将首次提供证据，证明嗜碱性粒细胞在 增强针对细菌的先天免疫反应，对于这个稀有的细胞群体来说，这是一个意想不到的作用。

PROJECT SUMMARY There are approximately 850,000 new cases of sepsis each year with mortality rates ranging from 240,000- 375,000. An impaired innate immune response can aggravate the septic condition by compromising the patient’s ability to combat an infection. However, the cells and mediators that enhance the innate immune response in sepsis are still unknown. Basophils account for less than 1% of peripheral blood leukocytes, which makes them the rarest known granulocytes. Basophils are evolutionarily conserved in many animal species, suggesting a beneficial rather than deleterious role of basophils. Nevertheless, it is unknown whether basophils play any role in the host’s defense against bacteria that can potentially prevent sepsis development. Our preliminary studies support such a role by showing that basophils are one of the very first cells to accumulate at the infection site at early stages of infection, and can improve survival and bacteria clearance in the polymicrobial model of sepsis induced by cecal ligation and puncture (CLP). We think that our findings in the murine system may be translatable to humans because we observed that trauma patients show increased numbers of basophils in circulation when a nosocomial infection was circumscribed to local tissues (early stages of infection) while basophil numbers decreased or remain unchanged when a patient developed a systemic infection (bacteremia) and was therefore at high risk of developing sepsis. Based on these studies, we hypothesize that basophils play a protective role in sepsis by enhancing the innate immune response against infection. Accordingly, we propose a research plan aimed at investigating the contribution of basophils to the innate immune response against bacteria. In Aim 1, we will identify mechanisms involved in basophil activation during an infection. We will use a genetic approach to investigate whether basophil stimulation through the TLR and MyD88 pathways is required to induce basophil activation and to confer protection during an infection; and we will examine whether the epithelial cell-derived cytokine, thymic stromal lymphopoietin (TSLP), can enhance the ability of basophils to respond to an infection. In Aim 2, we will define the mechanisms by which basophils confer protection against bacterial infections. Specifically, we will investigate interactions between basophils, the endothelium, and circulating leukocytes in a microvessel system and we will use mice with basophil-specific TNF deficiency to study these interactions during CLP. In Aim 3, we will establish the relevance of basophils in human infections and sepsis. Specifically, we will use mass cytometry (CyTOF) to assess basophil immune functions in samples collected from patients that develop nosocomial infections, mainly pneumonia, and we will establish whether these immune functions associate with clinical outcomes. We think that the studies proposed will expand our knowledge of sepsis physiopathology. Specifically, our studies will provide, for the first time, evidence for a critical role for basophils in the enhancement of the innate immune response against bacteria, an unexpected role for this rare cell population.