Epithelial HVEM maintains intraepithelial T cell survival and contributes to host protection

Intraepithelial T cells (IET) provide surveillance of the intestinal epithelium, but little is known about how epithelial-derived signals regulate IET. Analyzing mice with a deficiency for the herpes virus entry mediator (HVEM), a member of the TNF receptor superfamily (TNFRSF14), we showed HVEM maintains the survival of subsets of small intestine IET through interactions with TNFSF14 (LIGHT). RNA-seq and analysis of organoids showed that epithelial cell expressed HVEM provided signals that were required for optimal synthesis of collagen IV. Collagen IV supported IET survival in vitro via interactions with IET ß1 integrins. Furthermore, absence of ß1 integrin expression in T lymphocytes decreased TCR aß+ IET in vivo. Intravital microscopy showed that the patrolling movement of all IET was reduced without epithelial HVEM, and we hypothesize that collagen IV interactions with ß1 integrins could have been responsible. As likely consequences of decreased total IET number and movement, protective responses to Salmonella enterica were reduced in mice lacking either epithelial HVEM, HVEM binding partners CD160 or LIGHT, or ß1 integrins. Therefore, these data defined a circuit whereby epithelial HVEM regulated IET indirectly, through basement membrane synthesis that interacts with T cell integrins, with consequences for mucosal immunity. Overall design: mRNA from sorted proximal SI IEC or from sorted SI TCRab+CD8aa+ IET from Hvemfl/fl or Villin Cre x Hvemfl/fl mice

上皮内T细胞（Intraepithelial T cells, IET）负责对肠上皮实施免疫监视，但目前对于上皮来源信号调控IET的具体机制仍知之甚少。本研究针对肿瘤坏死因子受体超家族（TNFRSF14）成员——疱疹病毒进入介导因子（herpes virus entry mediator, HVEM）缺陷小鼠展开分析，结果显示HVEM可通过与肿瘤坏死因子超家族14（TNFSF14, LIGHT）的相互作用，维持小肠IET亚群的存活。RNA测序（RNA-seq）及类器官分析结果表明，上皮细胞表达的HVEM可介导关键信号，该信号对于IV型胶原的最优合成必不可少。体外实验证实，IV型胶原可通过与IET的β1整合素相互作用，支持IET的存活。进一步研究发现，T淋巴细胞中β1整合素表达缺失会导致体内T细胞受体αβ阳性（TCR αβ+）IET的数量显著减少。活体显微成像结果显示，缺失上皮HVEM后，所有IET的巡逻运动能力均出现下降，本研究推测该现象可能与IV型胶原与β1整合素的相互作用受损有关。鉴于总IET数量及运动能力下降可能带来的不良后果，缺失上皮HVEM、HVEM结合伴侣CD160或LIGHT，抑或是β1整合素的小鼠，其针对肠炎沙门氏菌（Salmonella enterica）的保护性免疫应答均出现减弱。综上，本研究明确了一条调控通路：上皮HVEM可通过调控基底膜合成，进而通过与T细胞整合素的相互作用间接调控IET，最终对黏膜免疫功能产生影响。整体实验设计：从Hvemfl/fl或Villin Cre×Hvemfl/fl小鼠中分选得到的近端小肠上皮细胞，或是分选的小肠TCRαβ+CD8αα+上皮内T细胞的mRNA