Pig-to-human xenotransplantation is rapidly approaching the clinical arena; however, it is unclear which immunomodulatory regimens will effectively control human immune responses to pig xenografts. We transplanted a gene-edited pig kidney into a brain-dead human recipient on pharmacologic immunosuppression and studied the human immune response to the xenograft using spatial transcriptomics and single-cell RNA sequencing. Human immune cells were uncommon in the porcine kidney cortex early after xenotransplantation and consisted of primarily myeloid cells. Both the porcine resident macrophages and human infiltrating macrophages expressed genes consistent with an alternatively activated, anti-inflammatory phenotype. No significant infiltration of human B or T cells into the porcine kidney xenograft was detected. Altogether, these findings provide proof of concept that conventional pharmacologic immunosuppression is sufficient to restrict infiltration of human immune cells into the xenograft early after compatible pig-to-human kidney xenotransplantation.

Summary Uterine natural killer cells are critical for pregnancy success, but the origin and development of these cells in humans remain unclear. Here we use various single cell approaches to identify the transcriptional programs governing uterine NK cell development in humans. These analyses suggest a developmental continuum which begins with seeding of the endometrium with blood immature CD56 bright precursors, evolves through CD56 bright endometrial founder NK cells, and ends with tissue resident decidual NK cells during pregnancy which possess non-cytotoxic functions. Our work identifies a role for sequential programs of tissue residency in the differentiation of these cells, as differentiating endometrial tissue resident NK (trNK) cells acquire early and late transcriptional programs of residency which coincide with acquisition of unique non-cytotoxic effector programs. Notably, we identified early residency programs in human endometrial trNKs by expression of NR4A2 , AP-1 transcription factors, and other immediate early response genes that were shared with CD8 tissue resident memory T cells in mice, suggesting conservation of transcriptional programs of early tissue residency programs across species and cell types. Late residency programs were guided by TGFβ, which promoted expression of various integrins and trNK subset diversification within the non-pregnant endometrium. Altogether, these data identify the molecular foundations for endometrial trNK heterogeneity and suggest that the uterine NK diversity observed during pregnancy is established before embryo implantation and intimately tied to residency programming.

Uterine natural killer cells (uNKs) are a tissue resident lymphocyte population that are critical for pregnancy success. Although mouse models have demonstrated that NK deficiency results in abnormal placentation and poor pregnancy outcomes, the generalizability of this knowledge to humans remains unclear. Here we identify uterus transplant (UTx) recipients as a human population with reduced uNK cells and altered pregnancy phenotypes. We show that the NK reduction in UTx correlates with impaired transcriptional programming of NK tissue residency arising from the inhibition of NFAT-mediated signaling. Our observations suggest that NFAT-dependent genes modulate multiple molecular tissue residency programs in uNKs. These include early residency programs involving AP-1-family transcription factors and TGF-β-mediated upregulation of surface integrins. Collectively, our data identify a previously undescribed role for NFAT in uterine NK tissue residency and provide novel mechanistic insights into the biologic basis of pregnancy complications due to alteration of tissue resident NK subsets in humans. One Sentence Summary:Role of NFAT in uterine NK cell tissue residency.

Abstract Tissue-resident uterine NK cells are essential for successful pregnancy, yet the molecular mechanisms guiding their tissue residency programming early after infiltration of blood-based precursors remain unknown. We examined the transition of CD56+ peripheral blood NK cells to a uterine resident state by performing scRNA-seq on enriched CD56+ cells from a matched peripheral blood (pb) and endometrial (e) biopsy taken during the secretory phase. Our integrated analysis comparing eNK vs pbNK cells identified a tissue adaptation signature. Key components of this signature included NR4A2 (94% vs 0%, p=9.46e-22), FOS (90% vs 9%, p=9.05e-14), and JUNB (77% vs 16%, p=3.15e-07) respectively. This signature also mirrored genes previously identified in activated murine intestinal CD8+ TRM cells early after LCMV infection. This signature was found in all endometrial CD56+ cells, including CD56bright CD16- eNKs, NKTs, and conventional eNKs (CD56dimCD16+). Pathway analysis implicated IL-17 and IL-18 cytokines, along with NFAT and VEGF signals in tissue residency programming. In conclusion, these data expand our understanding of early transcriptional programs in lymphocyte tissue adaptation, revealing the involvement of cytokines beyond TGF-β. Our data further indicate that signals associated with early tissue adaptation are conserved across species and cell types independent of an antigen receptor.

Uterine natural killer cells (uNK) are the most common human decidual lymphocytes, but the origin and ontogeny of uNKs remain unclear. Studies of human uterus transplant recipients (UTx) suggest that uNKs originate in the blood, but how these cells become tissue resident and differentiate into decidual NK cells is unknown. We studied the molecular mechanisms governing uNK tissue residency in human endometrium using single-cell RNA-seq and flow cytometry analyses. trNK cells with a CD49a+ CD16− phenotype were the most abundant CD56+ cells in the endometrium of 5 healthy control volunteers (HCs) [27±17% trNK vs. 4±2.7% CD49a− CD16+ conventional NK cells (cNK); p<0.02]. trNK cells differentially expressed genes associated with T cell tissue residency, such as ITGAE and ZNF683, compared to cNK. Although peripheral blood NK cells can express CD103 when incubated with TGF-β, trNKs upregulated CD103 expression in response to IL-15 alone in vitro. Given the dependency of CD103 expression on NFAT signals, we studied CD103 expression on trNKs by incubating human endometrium (n=7) with the calcineurin inhibitor FK506, which decreased IL-15-induced upregulation of CD103 (81% CD103+ [IL-15 alone] vs. 70% CD103− [IL-15 + FK506]; p=0.02). We next tested the in vivo relevance of these findings by comparing the frequency of trNKs in endometrial biopsies of five HCs with two biopsies of one UTx on FK506 immunosuppression. The UTx recipient had significantly fewer trNKs among CD45+ cells in two biopsies (HC: 27±17% vs. UTx: 4.3±2%; p=0.04). Altogether these findings suggest that IL-15-induced calcium signals influence uNK tissue residency, with significant implications for transplant recipients. This work was supported from UAB AMC21 and support of the uterus transplant program from the University of Alabama at Birmingham. P. Porrett is additionally supported by NIH R01 AI145905.

Uterine natural killer cells (uNKs) are critical mediators of pregnancy success, but how aberrancies in uNK survival or differentiation underpin pregnancy complications is unknown. To improve our understanding of normal and abnormal uNK biology, we studied 1) uNKs in uterus transplant (UTx) recipients at high risk for pregnancy complications and 2) uNK survival after exposure to pharmacologic immunosuppression in vitro. To address the first question, we analyzed uNKs isolated from endometrial biopsies of healthy controls (n=3) or UTx recipients (n=5) using scRNA-seq. In healthy controls, CD103-expressing uNK3 cells were the dominant uNK subset (30% of all uNK cells). In contrast, uNK1 cells were the most frequent (30%) in the majority of UTx recipients. This dominance of uNK1 cells in UTx recipients did not appear to arise only from loss of uNK3 cells, as the uNK1 transcriptional signature was abnormally upregulated in immature proliferating uNKs. Next, we used multiparameter flow cytometry to study single-cell suspensions of whole endometrium from deceased organ donors (n=4) that were cultured for one week with or without the calcineurin inhibitor FK506. Although FK506 significantly impaired the survival of CD103+ uNK3 cells in vitro, there was no evidence of uNK1 enhancement. Instead, FK506 appeared to selectively deplete CD39+ cells – a marker currently used to identify human decidual NK1 cells. Altogether, these results demonstrate that the distribution of uNK subsets is often altered in UTx recipients, and that FK506 can impact the survival of specific uNK subsets. Identification of the additional factors which impact uNK differentiation and survival will be necessary to understand the genesis of pregnancy complications. Supported by NIH/NIAID (R01 AI 145905) University of Pennsylvania Institute for Immunology

A radical solution is needed for the organ supply crisis, and the domestic pig is a promising organ source. In preparation for a clinical trial of xenotransplantation, we developed an in vivo pre-clinical human model to test safety and feasibility tenets established in animal models. After performance of a novel, prospective compatible crossmatch, we performed bilateral native nephrectomies in a human brain-dead decedent and subsequently transplanted two kidneys from a pig genetically engineered for human xenotransplantation. The decedent was hemodynamically stable through reperfusion, and vascular integrity was maintained despite the exposure of the xenografts to human blood pressure. No hyperacute rejection was observed, and the kidneys remained viable until termination 74 h later. No chimerism or transmission of porcine retroviruses was detected. Longitudinal biopsies revealed thrombotic microangiopathy that did not progress in severity, without evidence of cellular rejection or deposition of antibody or complement proteins. Although the xenografts produced variable amounts of urine, creatinine clearance did not recover. Whether renal recovery was impacted by the milieu of brain death and/or microvascular injury remains unknown. In summary, our study suggests that major barriers to human xenotransplantation have been surmounted and identifies where new knowledge is needed to optimize xenotransplantation outcomes in humans.