Thymic plasma cells as a source of protective natural antibodies in human neonates

项目总结 感染是全球新生儿死亡的主要原因之一。血清免疫被认为是 对地方性病原体最有效的第一道防线。理解这种保护性免疫是如何 在生命早期发展对于识别脆弱领域和设计抗击新生儿的战略至关重要 全球范围内的感染。然而，这一领域的研究还没有得到充分的探索。最近的几项研究表明，B细胞 免疫力是在胎儿时期开始形成的。例如，脐带血中存在的脐带血IgM来源于 完全来自胎儿。同样，来自胎儿的免疫球蛋白也存在于新生儿血液中，尽管 其确切浓度被母体免疫球蛋白的丰度所掩盖。总体而言，人们对 胎儿先天体液免疫的组成和谱系。这些东西的来源 胎儿体内的天然抗体也不清楚。肝和脾是B细胞在子宫内个体发育的重要部位 在胎儿时期，抗体产生细胞在这两个器官中的分化还没有报道。我们的 最近的研究揭示了新生儿体内另一种相当意想不到的天然抗体来源。我们 发现人类出生时的胸腺含有大量产生抗体的PC。这 子集是令人惊讶的异质性，包括产生所有类别和亚类免疫球蛋白的克隆 但IGD除外。此外，越来越多的证据支持这样一种观点，即这些PC存在差异 胸腺内通过一种机制仍未完全阐明。值得注意的是，约7%的新生儿PC 对所测试的7种致病菌和共生菌中至少有1种有反应。新生儿胸腺PC也富含 对凋亡细胞有反应的克隆，这是天然抗体的标志。总体而言，这些发现揭示了 人类胸腺作为人类新生儿天然抗体的意外来源。研究这些胸腺 因此，PC将提供一个难得的机会来研究人类的先天性体液免疫是如何发展的。这里, 我们进一步表征了新生儿胸腺PC群体的组成，并更具体地识别 优势克隆，这些克隆更有可能对先天血清学免疫做出贡献。研究还将 评估它们对细菌的反应性以及它们的保护能力。我们期待着这些研究 将为预防早期生命中感染的自然免疫防御的这一重要组成部分提供新的线索。 实验将在两个具体目标下进行： 目的1.鉴定新生儿优势胸腺浆细胞产生的NAB 目的2.评价新生儿胸腺浆细胞产生的NaBS的抗菌活性

PROJECT SUMMARY Infection is among the leading causes of neonatal deaths worldwide. Serological immunity is considered to be the most effective first line of defense against endemic pathogens. Understanding how this protective immunity develops in early life is essential to identify areas of vulnerability and design strategies to combat neonatal infections worldwide. This area of research however is underexplored. Several recent studies indicate that B cell immunity starts to develop during fetal life. For instance, cord blood IgM present in the cord blood originate exclusively from the fetus. Along the same line, IgG from fetal origin is also present in newborns blood although its exact concentration is masked by the abundance of maternal IgG. Overall, very little is known about the composition and repertoire of innate humoral immunity developed by the unborn child. The source of these natural antibodies in the fetus is also unclear. Liver and spleen are important sites of B cell ontogeny in utero but the differentiation of antibody-producing cells in these two organs during fetal life has not been reported. Our recent work revealed an alternate and rather unexpected source of natural antibodies in newborns. We uncovered that the human thymus at birth contains a significant contingent of antibody-producing PC. This subset is surprisingly heterogenous and includes clones producing all classes and subclasses of immunoglobulin with the exception of IgD. Furthermore, converging lines of evidence support the view that these PC differentiate intrathymically through a mechanism that remains to be fully elucidated. Remarkably, ~7% of neonatal PC reacted to at least 1 of 7 pathogenic and commensal bacteria tested. Neonatal thymic PC were also enriched in clones reactive to apoptotic cells, a hallmark of natural antibodies. Collectively, these findings exposed the human thymus as an unsuspected source of natural antibodies in human newborns. Investigating these thymic PC will therefore provide a rare opportunity to examine how innate humoral immunity develops in humans. Here, we further characterize the composition of neonatal thymic PC populations and more specifically identify predominant clones which were more likely to have contributed to innate serological immunity. Studies will also assess their reactivity profile toward bacteria as well as their protective capabilities. We anticipate these studies will shed new light on this essential component of natural immune defenses against infections in early life. Experiments will be carried out in two specific aims: Aim 1. To characterize Nabs produced by dominant neonatal thymic plasma cells Aim 2. To assess antibacterial activity of Nabs produced by neonatal thymic plasma cells