Human tissue-resident CD8 T cells contribute to trophoblast homeostasis in health and during acute inflammation.

Previous studies have highlighted that some T cell subsets in tissues can provide signals to support tissue cell homeostasis and differentiation. If and how T cell-tissue cell signaling is altered in healthy compared to inflamed tissues is poorly understood. Here, we address if communication between human T cells and tissue cells changes from steady state to an acutely inflamed state in the human placenta. We used single cell analysis strategies to examine invasive cytotrophoblasts (iCTBs) and immune cells isolated from third trimester healthy and acutely inflamed human placentas. We performed cell communication analysis to predict cell-cell communication networks, and found evidence that iCTBs provided signals to support the recruitment of T cells, as well as the formation of tissue-resident memory CD8 T cells (Trm). In exchange, Trm provide signals to support iCTB homeostasis. During acute inflammation, iCTBs and macrophages underwent profound transcriptional changes, while most T cell subsets only underwent limited transcriptional changes. This was not due to T cell exhaustion or tolerance, as T cells were functionally intact. Cell communication analysis and validation at the protein level provide evidence that T cells can maintain their homeostatic support to iCTBs during acute inflammation.