Tissue Determinants of Human NK Cell Development, Function, and Residence.

Immune responses in diverse tissue sites are critical for protective immunity and homeostasis. Here, we investigate how tissue localization regulates the development and function of human natural killer (NK) cells, innate lymphocytes important for anti-viral and tumor immunity. Integrating high-dimensional analysis of NK cells from blood, lymphoid organs, and mucosal tissue sites from 60 individuals, we identify tissue-specific patterns of NK cell subset distribution, maturation, and function maintained across age and between individuals. Mature and terminally differentiated NK cells with enhanced effector function predominate in blood, bone marrow, spleen, and lungs and exhibit shared transcriptional programs across sites. By contrast, precursor and immature NK cells with reduced effector capacity populate lymph nodes and intestines and exhibit tissue-resident signatures and site-specific adaptations. Together, our results reveal anatomic control of NK cell development and maintenance as tissue-resident populations, whereas mature, terminally differentiated subsets mediate immunosurveillance through diverse peripheral sites. VIDEO ABSTRACT.

Tissue-Resident Memory T Cells Mediate Immune Homeostasis in the Human Pancreas through the PD-1/PD-L1 Pathway.

Non-recirculating tissue-resident memory T cells (TRMs) are the predominant T cell subset in diverse tissue sites, where they mediate protective immune responses in situ. Here, we reveal a role for TRM in maintaining immune homeostasis in the human pancreas through interactions with resident macrophages and the PD-1/PD-L1 inhibitory pathway. Using tissues obtained from organ donors, we identify that pancreas T cells comprise CD8+PD-1hi TRMs, which are phenotypically, functionally, and transcriptionally distinct compared to TRMs in neighboring jejunum and lymph node sites. Pancreas TRMs cluster with resident macrophages throughout the exocrine areas; TRM effector functions are enhanced by macrophage-derived co-stimulation and attenuated by the PD-1/PD-L1 pathways. Conversely, in samples from chronic pancreatitis, TRMs exhibit reduced PD-1 expression and reduced interactions with macrophages. These findings suggest important roles for PD-1 and TRM-macrophage interactions in controlling tissue homeostasis and immune dysfunctions underlying inflammatory disease, with important implications for PD-1-based immunotherapies.

Deceased Brain Dead Donor Liver Transplantation and Utilization in the United States: Nighttime and Weekend Effects.

BACKGROUND: Understanding factors that contribute to liver discards and nonusage is urgently needed to improve organ utilization. METHODS: Using Scientific Registry of Transplant Recipient data, we studied a national cohort of all US adult, deceased brain dead donor, isolated livers available for transplantation from 2003 to 2016, including organ-specific and system-wide factors that may affect organ procurement and discard rates. RESULTS: Of 73 686 available livers, 65 316 (88.64%) were recovered for transplant, of which 6454 (9.88%) were ultimately discarded. Livers that were not procured or, on recovery, discarded were more frequently from older, heavier, hepatitis B virus (HCV)+, and more comorbid donors (P < 0.001). However, even after adjustment for organ quality, the odds of liver nonusage were 11% higher on the weekend (defined as donor procurements with cross-clamping occurring from 5:00 PM Friday until 11:59 AM Sunday) compared with weekdays (P < 0.001). Nonuse rates were also higher at night (P < 0.001), defined as donor procurements with cross-clamping occurring from 5:00 PM to 5:00 AM; however, weekend nights had significantly higher nonuse rates compared with weekday nights (P = 0.005). After Share 35, weekend nonusage rates decreased from 21.77% to 19.51% but were still higher than weekday nonusage rates (P = 0.065). Weekend liver nonusage was higher in all 11 United Network of Organ Sharing regions, with an absolute average of 2.00% fewer available livers being used on the weekend compared with weekdays. CONCLUSIONS: Although unused livers frequently have unfavorable donor characteristics, there are also systemic and operational factors, including time of day and day of the week a liver becomes available, that impact the chance of liver nonprocurement and discard.

Microanatomical dissection of human intestinal T-cell immunity reveals site-specific changes in gut-associated lymphoid tissues over life.

Defining adaptive immunity with the complex structures of the human gastrointestinal (GI) tract over life is essential for understanding immune responses to ingested antigens, commensal and pathogenic microorganisms, and dysfunctions in disease. We present here an analysis of lymphocyte localization and T cell subset composition across the human GI tract including mucosal sites (jejunum, ileum, colon), gut-associated lymphoid tissues (isolated lymphoid follicles (ILFs), Peyer's patches (PPs), appendix), and mesenteric lymph nodes (MLNs) from a total of 68 donors spanning eight decades of life. In pediatric donors, ILFs and PP containing naïve T cells and regulatory T cells (Tregs) are prevalent in the jejunum and ileum, respectively; these decline in frequency with age, contrasting stable frequencies of ILFs and T cell subsets in the colon. In the mucosa, tissue resident memory T cells develop during childhood, and persist in high frequencies into advanced ages, while T cell composition changes with age in GALT and MLN. These spatial and temporal features of human intestinal T cell immunity define signatures that can be used to train predictive machine learning algorithms. Our findings demonstrate an anatomic basis for age-associated alterations in immune responses, and establish a quantitative baseline for intestinal immunity to define disease pathologies.

Functional heterogeneity of human tissue-resident memory T cells based on dye efflux capacities.

Tissue-resident memory T cells (TRMs) accelerate pathogen clearance through rapid and enhanced functional responses in situ. TRMs are prevalent in diverse anatomic sites throughout the human lifespan, yet their phenotypic and functional diversity has not been fully described. Here, we identify subpopulations of human TRMs based on the ability to efflux fluorescent dyes [efflux(+) TRMs] located within mucosal and lymphoid sites with distinct transcriptional profiles, turnover, and functional capacities. Compared with efflux(-) TRMs, efflux(+) TRMs showed transcriptional and phenotypic features of quiescence including reduced turnover, decreased expression of exhaustion markers, and increased proliferative capacity and signaling in response to homeostatic cytokines. Moreover, upon activation, efflux(+) TRMs secreted lower levels of inflammatory cytokines such as IFN-γ and IL-2 and underwent reduced degranulation. Interestingly, analysis of TRM subsets following activation revealed that both efflux(+) and efflux(-) TRMs undergo extensive transcriptional changes following TCR ligation but retain core TRM transcriptional properties including retention markers, suggesting that TRMs carry out effector function in situ. Overall, our results suggest a model for tissue-resident immunity wherein heterogeneous subsets have differential capacities for longevity and effector function.

Human Lymph Nodes Maintain TCF-1hi Memory T Cells with High Functional Potential and Clonal Diversity throughout Life.

Translating studies on T cell function and modulation from mouse models to humans requires extrapolating in vivo results on mouse T cell responses in lymphoid organs (spleen and lymph nodes [LN]) to human peripheral blood T cells. However, our understanding of T cell responses in human lymphoid sites and their relation to peripheral blood remains sparse. In this study, we used a unique human tissue resource to study human T cells in different anatomical compartments within individual donors and identify a subset of memory CD8+ T cells in LN, which maintain a distinct differentiation and functional profile compared with memory CD8+ T cells in blood, spleen, bone marrow, and lungs. Whole-transcriptome and high-dimensional cytometry by time-of-flight profiling reveals that LN memory CD8+ T cells express signatures of quiescence and self-renewal compared with corresponding populations in blood, spleen, bone marrow, and lung. LN memory T cells exhibit a distinct transcriptional signature, including expression of stem cell-associated transcription factors TCF-1 and LEF-1, T follicular helper cell markers CXCR5 and CXCR4, and reduced expression of effector molecules. LN memory T cells display high homology to a subset of mouse CD8+ T cells identified in chronic infection models that respond to checkpoint blockade immunotherapy. Functionally, human LN memory T cells exhibit increased proliferation to TCR-mediated stimulation and maintain higher TCR clonal diversity compared with memory T cells from blood and other sites. These findings establish human LN as reservoirs for memory T cells with high capacities for expansion and diverse recognition and important targets for immunotherapies.

Factors leading to the discard of deceased donor kidneys in the United States.

The proportion of deceased donor kidneys procured for transplant but subsequently discarded has been growing steadily in the United States, but factors contributing to the rising discard rate remain unclear. To assess the reasons for and probability of organ discard we assembled a cohort of 212,305 deceased donor kidneys recovered for transplant from 2000-2015 in the SRTR registry that included 36,700 kidneys that were discarded. 'Biopsy Findings' (38.2%) was the most commonly reported reason for discard. The median Kidney Donor Risk Index of discarded kidneys was significantly higher than transplanted organs (1.78 vs 1.12), but a large overlap in the quality of discarded and transplanted kidneys was observed. Kidneys of donors who were older, female, Black, obese, diabetic, hypertensive or HCV-positive experienced a significantly increased odds of discard. Kidneys from donors with multiple unfavorable characteristics were more likely to be discarded, whereas unilaterally discarded kidneys had the most desirable donor characteristics and the recipients of their partner kidneys experienced a one-year death-censored graft survival rate over 90%. There was considerable geographic variation in the odds of discard across the United States, which further supports the notion that factors beyond organ quality contributed to kidney discard. Thus, while the discard of a small fraction of organs procured from donors may be inevitable, the discard of potentially transplantable kidneys needs to be avoided. This will require a better understanding of the factors contributing to organ discard in order to remove the disincentives to utilize less-than-ideal organs for transplantation.

Human Tissue-Resident Memory T Cells Are Defined by Core Transcriptional and Functional Signatures in Lymphoid and Mucosal Sites.

Tissue-resident memory T cells (TRMs) in mice mediate optimal protective immunity to infection and vaccination, while in humans, the existence and properties of TRMs remain unclear. Here, we use a unique human tissue resource to determine whether human tissue memory T cells constitute a distinct subset in diverse mucosal and lymphoid tissues. We identify a core transcriptional profile within the CD69+ subset of memory CD4+ and CD8+ T cells in lung and spleen that is distinct from that of CD69- TEM cells in tissues and circulation and defines human TRMs based on homology to the transcriptional profile of mouse CD8+ TRMs. Human TRMs in diverse sites exhibit increased expression of adhesion and inhibitory molecules, produce both pro-inflammatory and regulatory cytokines, and have reduced turnover compared with circulating TEM, suggesting unique adaptations for in situ immunity. Together, our results provide a unifying signature for human TRM and a blueprint for designing tissue-targeted immunotherapies.

An atlas of B-cell clonal distribution in the human body.

B-cell responses result in clonal expansion, and can occur in a variety of tissues. To define how B-cell clones are distributed in the body, we sequenced 933,427 B-cell clonal lineages and mapped them to eight different anatomic compartments in six human organ donors. We show that large B-cell clones partition into two broad networks-one spans the blood, bone marrow, spleen and lung, while the other is restricted to tissues within the gastrointestinal (GI) tract (jejunum, ileum and colon). Notably, GI tract clones display extensive sharing of sequence variants among different portions of the tract and have higher frequencies of somatic hypermutation, suggesting extensive and serial rounds of clonal expansion and selection. Our findings provide an anatomic atlas of B-cell clonal lineages, their properties and tissue connections. This resource serves as a foundation for studies of tissue-based immunity, including vaccine responses, infections, autoimmunity and cancer.

Dendritic Cells Display Subset and Tissue-Specific Maturation Dynamics over Human Life.

Maturation and migration to lymph nodes (LNs) constitutes a central paradigm in conventional dendritic cell (cDC) biology but remains poorly defined in humans. Using our organ donor tissue resource, we analyzed cDC subset distribution, maturation, and migration in mucosal tissues (lungs, intestines), associated lymph nodes (LNs), and other lymphoid sites from 78 individuals ranging from less than 1 year to 93 years of age. The distribution of cDC1 (CD141hiCD13hi) and cDC2 (Sirp-α+CD1c+) subsets was a function of tissue site and was conserved between donors. We identified cDC2 as the major mature (HLA-DRhi) subset in LNs with the highest frequency in lung-draining LNs. Mature cDC2 in mucosal-draining LNs expressed tissue-specific markers derived from the paired mucosal site, reflecting their tissue-migratory origin. These distribution and maturation patterns were largely maintained throughout life, with site-specific variations. Our findings provide evidence for localized DC tissue surveillance and reveal a lifelong division of labor between DC subsets, with cDC2 functioning as guardians of the mucosa.

Apical Aortic Conduit Infection 27 Years After Repaired Left Ventricular Outflow Tract Obstruction.

Left ventricle to aortic conduits were used for the treatment of complex left ventricular outflow tract obstruction in the pediatric population in the mid-1970s. Although this technique has been largely replaced by the Ross-Konno procedure, many patients still have functioning apicoaortic conduits in place today. Few clinical reports or case series exist in pediatric cohorts documenting the natural history or potential long-term complications of this prosthesis. In this report, we describe our experience managing a patient with Shone's syndrome and an apical aortic porcine-valved conduit remnant that became infected 17 years postconduit valve excision for valvular insufficiency.

Injury-related hospital admissions of military dependents compared with similarly aged nonmilitary insured infants, children, and adolescents.

BACKGROUND: Military deployment of one or both parents is associated with declines in school performance, behavioral difficulties, and increases in reported mental health conditions, but less is known regarding injury risks in pediatric military dependents. METHODS: Kid Health Care Cost and Utilization Project 2006 (KID) was used to identify military dependents aged 0.1 year to 17 years through expected insurance payer being CHAMPUS, Tricare, or CHAMPVA (n = 12,310) and similarly aged privately insured nonmilitary in CHAMPUS, Tricare, or CHAMPVA states (n = 730,065). Mental health diagnoses per 1,000 hospitalizations and mechanisms of injury per 1,000 injury-related hospitalizations are reported. Unweighted univariate analyses used Fisher's exact, χ(2), and analysis of variance tests for significance. Odds ratios are age and sex adjusted with 95% confidence intervals. RESULTS: Injury-related admissions were higher in military than in nonmilitary dependents (15.5% vs. 13.2%, p < 0.0001). Age- and sex-adjusted motor vehicle occupant and pedestrian injuries were significantly lower in all-age military dependents but not in age-stratified categories. Very young military dependents had higher all-cause injury admissions (p < 0.0001), drowning/near drowning (p < 0.0001), and intracranial injury (p < 0.0001) and showed a tendency toward higher suffocation (p = 0.055) and crushing injury (p = 0.065). Military adolescents and teenagers had higher suicide/suicide attempts (p = 0.0001) and poisonings from medicinal substances (p = 0.0001). Mental health diagnoses were significantly higher in every age category of military dependents. All-cause in-hospital mortality tended to be greater in military than in nonmilitary dependents (p = 0.052). CONCLUSION: This study suggests that military dependents are a vulnerable population with special needs and provides clues to areas where injury prevention professionals might begin to address their needs. LEVEL OF EVIDENCE: Prognostic/epidemiologic study, level II.