In the epididymis, prevention of autoimmune responses against spermatozoa and simultaneous protection against pathogens is important for male fertility. We have previously shown that mononuclear phagocytes (MPs) are located either in the epididymal interstitium or in close proximity to the epithelium. In the initial segments (IS), these 'intraepithelial' MPs extend slender luminal-reaching projections between epithelial cells. In this study, we performed an in-depth characterisation of MPs isolated from IS, caput-corpus and cauda epididymis of CX3CR1EGFP+/- mice that express EGFP in these cells. Flow cytometry analysis revealed region-specific subsets of MPs that express combinations of markers traditionally described in 'dendritic cells' or 'macrophages'. RNA sequencing identified distinct transcriptomic signatures in MPs from each region and revealed specific genes involved in inflammatory and anti-inflammatory responses, phagosomal activity and antigen processing and presentation. Functional fluorescent in vivo labelling assays showed that higher percentages of CX3CR1+ MPs that captured and processed antigens were detected in the IS compared to other regions. Confocal microscopy showed that in the IS, caput and corpus, circulatory antigens were internalised and processed by interstitial and intraepithelial MPs. However, in the cauda only interstitial MPs internalised and processed antigens, while intraepithelial MPs did not take up antigens, indicating that all antigens have been captured before they reached the epithelial lining. Cauda MPs may thus confer a stronger protection against blood-borne pathogens compared to proximal regions. By identifying immunoregulatory mechanisms in the epididymis, our study may lead to new therapies for male infertility and epididymitis and identify potential targets for immunocontraception.

中文翻译：

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附睾中单核吞噬细胞的区域特异性转录组和功能特征。

在附睾中，预防针对精子的自身免疫反应并同时保护免受病原体的侵害对于男性生育能力很重要。我们之前已经表明，单核吞噬细胞 (MPs) 位于附睾间质或靠近上皮。在初始段 (IS)，这些“上皮内” MP 在上皮细胞之间延伸细长的管腔到达投影。在这项研究中，我们对从在这些细胞中表达 EGFP 的 CX3CR1EGFP+/- 小鼠的 IS、头体和附睾尾分离的 MPs 进行了深入表征。流式细胞术分析揭示了表达传统上在“树突细胞”或“巨噬细胞”中描述的标记组合的 MP 的区域特异性亚群。RNA 测序在每个区域的 MP 中鉴定出不同的转录组特征，并揭示了参与炎症和抗炎反应、吞噬体活性以及抗原加工和呈递的特定基因。功能性荧光体内标记测定表明，与其他区域相比，在 IS 中检测到捕获和处理抗原的 CX3CR1+ MPs 的百分比更高。共聚焦显微镜显示，在 IS、头和体中，循环抗原被间质和上皮内 MPs 内化和加工。然而，在马尾仅间质 MPs 内化和加工抗原，而上皮内 MPs 不吸收抗原，表明所有抗原在到达上皮衬里之前已被捕获。因此，与近端区域相比，Cauda MPs 可能对血液传播的病原体提供更强的保护。通过确定附睾中的免疫调节机制，我们的研究可能会导致男性不育症和附睾炎的新疗法，并确定免疫避孕的潜在靶点。