The bladder is a major component of the urinary tract, an organ system that expels metabolic waste and excess water, which necessitates proximity to the external environment and its pathogens. It also houses a commensal microbiome. Therefore, its tissue immunity must resist pathogen invasion while maintaining tolerance to commensals. Bacterial infection of the bladder is common, with half of women globally experiencing one or more episodes of cystitis in their lifetime. Despite this, our knowledge of bladder immunity, particularly in humans, is incomplete. Here we consider the current view of tissue immunity in the bladder, with a focus on defense against infection. The urothelium has robust immune functionality, and its defensive capabilities are supported by resident immune cells, including macrophages, dendritic cells, natural killer cells, and γδ T cells. We discuss each in turn and consider why adaptive immune responses are often ineffective in preventing recurrent infection, as well as areas of priority for future research.

中文翻译：

---

膀胱的组织免疫

膀胱是泌尿道的主要组成部分，泌尿道是排出代谢废物和多余水分的器官系统，因此需要接近外部环境及其病原体。它还拥有共生微生物组。因此，其组织免疫必须抵抗病原体入侵，同时保持对共生体的耐受性。膀胱细菌感染很常见，全球有一半的女性一生中经历过一次或多次膀胱炎。尽管如此，我们对膀胱免疫的了解，特别是人类的膀胱免疫，仍然不完整。在这里，我们考虑目前对膀胱组织免疫的看法，重点是防御感染。尿路上皮具有强大的免疫功能，其防御能力得到常驻免疫细胞的支持，包括巨噬细胞、树突状细胞、自然杀伤细胞和γδ T细胞。我们依次讨论每个问题，并考虑为什么适应性免疫反应在预防复发感染方面通常无效，以及未来研究的优先领域。