Sexual dimorphism in skin immunity is mediated by an androgen-ILC2-dendritic cell axis

Males and females exhibit profound differences in immune responses and disease susceptibility. However, the factors responsible for sex differences in tissue immunity remain poorly understood. Here, we uncovered a dominant role for type 2 innate lymphoid cells (ILC2s) in shaping sexual immune dimorphism within the skin. Mechanistically, negative regulation of ILC2s by androgens leads to a reduction in dendritic cell accumulation and activation in males, along with reduced tissue immunity. Collectively, our results reveal a role for the androgen-ILC2-dendritic cell axis in controlling sexual immune dimorphism. Moreover, this work proposes that tissue immune set points are defined by the dual action of sex hormones and the microbiota, with sex hormones controlling the strength of local immunity and microbiota calibrating its tone.

The neuroimmune CGRP-RAMP1 axis tunes cutaneous adaptive immunity to the microbiota

The somatosensory nervous system surveils external stimuli at barrier tissues, regulating innate immune cells under infection and inflammation. The roles of sensory neurons in controlling the adaptive immune system, and more specifically immunity to the microbiota, however, remain elusive. Here, we identified a mechanism for direct neuroimmune communication between commensal-specific T lymphocytes and somatosensory neurons mediated by the neuropeptide calcitonin gene-related peptide (CGRP) in the skin. Intravital imaging revealed that commensal-specific T cells are in close proximity to cutaneous nerve fibers in vivo. Correspondingly, we observed upregulation of the receptor for the neuropeptide CGRP, RAMP1, in CD8+ T lymphocytes induced by skin commensal colonization. The neuroimmune CGRP-RAMP1 signaling axis functions in commensal-specific T cells to constrain Type 17 responses and moderate the activation status of microbiota-reactive lymphocytes at homeostasis. As such, modulation of neuroimmune CGRP-RAMP1 signaling in commensal-specific T cells shapes the overall activation status of the skin epithelium, thereby impacting the outcome of responses to insults such as wounding. The ability of somatosensory neurons to control adaptive immunity to the microbiota via the CGRP-RAMP1 axis underscores the various layers of regulation and multisystem coordination required for optimal microbiota-reactive T cell functions under steady state and pathology.

The neuroimmune CGRP-RAMP1 axis tunes cutaneous adaptive immunity to the microbiota

The somatosensory nervous system surveils external stimuli at barrier tissues, regulating innate immune cells under infection and inflammation. The roles of sensory neurons in controlling the adaptive immune system, and more specifically immunity to the microbiota, however, remain elusive. Here, we identified a novel mechanism for direct neuroimmune communication between commensal-specific T lymphocytes and somatosensory neurons mediated by the neuropeptide Calcitonin Gene-Related Peptide (CGRP) in the skin. Intravital imaging revealed that commensal-specific T cells are in close proximity to cutaneous nerve fibers in vivo . Correspondingly, we observed upregulation of the receptor for the neuropeptide CGRP, RAMP1, in CD8 + T lymphocytes induced by skin commensal colonization. Neuroimmune CGRP-RAMP1 signaling axis functions in commensal-specific T cells to constrain Type 17 responses and moderate the activation status of microbiota-reactive lymphocytes at homeostasis. As such, modulation of neuroimmune CGRP-RAMP1 signaling in commensal-specific T cells shapes the overall activation status of the skin epithelium, thereby impacting the outcome of responses to insults such as wounding. The ability of somatosensory neurons to control adaptive immunity to the microbiota via the CGRP-RAMP1 axis underscores the various layers of regulation and multisystem coordination required for optimal microbiota-reactive T cell functions under steady state and pathology.

Significance statement

Multisystem coordination at barrier surfaces is critical for optimal tissue functions and integrity, in response to microbial and environmental cues. In this study, we identified a novel neuroimmune crosstalk mechanism between the sensory nervous system and the adaptive immune response to the microbiota, mediated by the neuropeptide CGRP and its receptor RAMP1 on skin microbiota-induced T lymphocytes. The neuroimmune CGPR-RAMP1 axis constrains adaptive immunity to the microbiota and overall limits the activation status of the skin epithelium, impacting tissue responses to wounding. Our study opens the door to a new avenue to modulate adaptive immunity to the microbiota utilizing neuromodulators, allowing for a more integrative and tailored approach to harnessing microbiota-induced T cells to promote barrier tissue protection and repair.

Divergent molecular networks program functionally distinct CD8+ skin-resident memory T cells

Skin-resident CD8+ T cells include distinct interferon-γ-producing [tissue-resident memory T type 1 (TRM1)] and interleukin-17 (IL-17)-producing (TRM17) subsets that differentially contribute to immune responses. However, whether these populations use common mechanisms to establish tissue residence is unknown. In this work, we show that TRM1 and TRM17 cells navigate divergent trajectories to acquire tissue residency in the skin. TRM1 cells depend on a T-bet-Hobit-IL-15 axis, whereas TRM17 cells develop independently of these factors. Instead, c-Maf commands a tissue-resident program in TRM17 cells parallel to that induced by Hobit in TRM1 cells, with an ICOS-c-Maf-IL-7 axis pivotal to TRM17 cell commitment. Accordingly, by targeting this pathway, skin TRM17 cells can be ablated without compromising their TRM1 counterparts. Thus, skin-resident T cells rely on distinct molecular circuitries, which can be exploited to strategically modulate local immunity.

Let-7 enhances murine anti-tumor CD8 T cell responses by promoting memory and antagonizing terminal differentiation

The success of the CD8 T cell-mediated immune response against infections and tumors depends on the formation of a long-lived memory pool, and the protection of effector cells from exhaustion. The advent of checkpoint blockade therapy has significantly improved anti-tumor therapeutic outcomes by reversing CD8 T cell exhaustion, but fails to generate effector cells with memory potential. Here, using in vivo mouse models, we show that let-7 miRNAs determine CD8 T cell fate, where maintenance of let-7 expression during early cell activation results in memory CD8 T cell formation and tumor clearance. Conversely, let-7-deficiency promotes the generation of a terminal effector population that becomes vulnerable to exhaustion and cell death in immunosuppressive environments and fails to reject tumors. Mechanistically, let-7 restrains metabolic changes that occur during T cell activation through the inhibition of the PI3K/AKT/mTOR signaling pathway and production of reactive oxygen species, potent drivers of terminal differentiation and exhaustion. Thus, our results reveal a role for let-7 in the time-sensitive support of memory formation and the protection of effector cells from exhaustion. Overall, our data suggest a strategy in developing next-generation immunotherapies by preserving the multipotency of effector cells rather than enhancing the efficacy of differentiation.

Pathogenic Th17 cell differentiation is negatively regulated by let-7 microRNAs in a mouse model of multiple sclerosis

Autoimmune disorders such as multiple sclerosis (MS) are caused by proinflammatory events mediated by pathogenic Th17 cells. In MS, these cells arise in response to autoantigen recognition and exposure to the cytokines IL-1β and IL-23, migrate to the central nervous system (CNS) by following gradients of CCR2- and CCR5-cognate chemokines, and secrete GM-CSF. GM-CSF is essential for disease development, as it promotes the activation, differentiation, and recruitment of peripheral inflammatory myeloid cells to the CNS that directly demyelinate neurons and damage axons. Th17 cell pathogenicity in MS has been correlated with microRNA (miRNA) dysregulation, which leads to aberrant post-transcriptional regulation of gene expression and enhanced autoreactive phenotype. We found that the lethal-7 (let-7) miRNA family is abundantly expressed in naive CD4+ T cells, but gets dramatically downregulated over time following antigen encounter, indicating that let-7 may control the differentiation of pathogenic Th17 cells. To investigate a potential regulatory role for let-7 in Th17 cell autoreactivity, we used experimental autoimmune encephalomyelitis (EAE), the animal model of MS. Specifically, we demonstrated that let-7 confers protection from EAE by negatively regulating the proliferation, IL-1β/IL-23-dependent differentiation, and CCR2/CCR5-dependent migration of pathogenic Th17 cells to the CNS. Conversely, absence of let-7 led to enhanced Th17 cell autoreactivity and aggravated disease. Therefore, our results identify a novel regulatory role for let-7 miRNAs in pathogenic Th17 differentiation during EAE development, suggesting a promising therapeutic application for the treatment of MS-related autoimmune diseases.

Non-coding RNAs in CD8 T cell biology

CD8 T cells are among the most vigorous soldiers of the immune system that fight viral infections and cancer. CD8 T cell development, maintenance, activation and differentiation are under the tight control of multiple transcriptional and post-transcriptional networks. Over the last two decades it has become clear that non-coding RNAs (ncRNAs), which consist of microRNAs (miRNAs) and long ncRNAs (lncRNAs), have emerged as global biological regulators. While our understanding of the function of specific miRNAs has increased since the discovery of RNA interference, it is still very limited, and the field of lncRNAs is just starting to blossom. Here we will summarize our knowledge on the role of ncRNAs in CD8 T cell biology, including differentiation into memory and exhausted cells.

Differentiation of Pathogenic Th17 Cells Is Negatively Regulated by Let-7 MicroRNAs in a Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is a disabling demyelinating autoimmune disorder of the central nervous system (CNS) which is driven by IL-23- and IL-1β-induced autoreactive Th17 cells that traffic to the CNS and secrete proinflammatory cytokines. Th17 pathogenicity in MS has been correlated with the dysregulation of microRNA (miRNA) expression, and specific miRNAs have been shown to promote the pathogenic Th17 phenotype. In the present study, we demonstrate, using the animal model of MS, experimental autoimmune encephalomyelitis (EAE), that let-7 miRNAs confer protection against EAE by negatively regulating the proliferation, differentiation and chemokine-mediated migration of pathogenic Th17 cells to the CNS. Specifically, we found that let-7 miRNAs may directly target the cytokine receptors Il1r1 and Il23r, as well as the chemokine receptors Ccr2 and Ccr5. Therefore, our results identify a novel regulatory role for let-7 miRNAs in pathogenic Th17 differentiation during EAE development, suggesting a promising therapeutic application for disease treatment.

Survival of Naïve T Cells Requires the Expression of Let-7 miRNAs

Maintaining the diversity and constant numbers of naïve T cells throughout the organism's lifetime is necessary for efficient immune responses. Naïve T cell homeostasis, which consists of prolonged survival, occasional proliferation and enforcement of quiescence, is tightly regulated by multiple signaling pathways which are in turn controlled by various transcription factors. However, full understanding of the molecular mechanisms underlying the maintenance of the peripheral T cell pool has not been achieved. In the present study, we demonstrate that T cell-specific deficiency in let-7 miRNAs results in peripheral T cell lymphopenia resembling that of Dicer1 knockout mice. Deletion of let-7 leads to profound T cell apoptosis while overexpression prevents it. We further show that in the absence of let-7, T cells cannot sustain optimal levels of the pro-survival factor Bcl2 in spite of the intact IL-7 signaling, and re-expression of Bcl2 in let-7 deficient T cells completely rescues the survival defect. Thus, we have uncovered a novel let-7-dependent mechanism of post-transcriptional regulation of naïve T cell survival in vivo.

Modulation of let-7 miRNAs controls the differentiation of effector CD8 T cells

The differentiation of naive CD8 T cells into effector cytotoxic T lymphocytes upon antigen stimulation is necessary for successful antiviral, and antitumor immune responses. Here, using a mouse model, we describe a dual role for the let-7 microRNAs in the regulation of CD8 T cell responses, where maintenance of the naive phenotype in CD8 T cells requires high levels of let-7 expression, while generation of cytotoxic T lymphocytes depends upon T cell receptor-mediated let-7 downregulation. Decrease of let-7 expression in activated T cells enhances clonal expansion and the acquisition of effector function through derepression of the let-7 targets, including Myc and Eomesodermin. Ultimately, we have identified a novel let-7-mediated mechanism, which acts as a molecular brake controlling the magnitude of CD8 T cell responses.

DOI:http://dx.doi.org/10.7554/eLife.26398.001

Expansion of the kidney donor pool by using cardiac death donors with prolonged time to cardiorespiratory arrest

Donation after Cardiac Death (DCD) is an increasingly important source of kidney transplants, but because of concerns of ischemic injury during the agonal phase, many centers abandon donation if cardiorespiratory arrest has not occurred within 1 h of controlled withdrawal of life-supporting treatment (WLST). We report the impact on donor numbers and transplant function using instead a minimum 'cut-off' time of 4 h. The agonal phase of 173 potential DCD donors was characterized according to the presence or absence of: acidemia; lactic acidosis; prolonged (>30 min) hypotension, hypoxia or oliguria, and the impact of these characteristics on 3- and 12-month transplant outcome evaluated by multivariable regression analysis. Of the 117 referrals who became donors, 27 (23.1%) arrested more than 1 h after WLST. Longer agonal-phase times were associated with greater donor instability, but surprisingly neither agonal-phase instability nor its duration influenced transplant outcome. In contrast, 3- and 12-month eGFR in the 190 transplanted kidneys was influenced independently by donor age, and 3-month eGFR by cold ischemic time. DCD kidney numbers are increased by 30%, without compromising transplant outcome, by lengthening the minimum waiting time after WLST from 1 to 4 h.

Expansion of the kidney donor pool by using cardiac death donors with prolonged time to cardiorespiratory arrest

Donation after Cardiac Death (DCD) is an increasingly important source of kidney transplants, but because of concerns of ischemic injury during the agonal phase, many centers abandon donation if cardiorespiratory arrest has not occurred within 1 h of controlled withdrawal of life-supporting treatment (WLST). We report the impact on donor numbers and transplant function using instead a minimum 'cut-off' time of 4 h. The agonal phase of 173 potential DCD donors was characterized according to the presence or absence of: acidemia; lactic acidosis; prolonged (>30 min) hypotension, hypoxia or oliguria, and the impact of these characteristics on 3- and 12-month transplant outcome evaluated by multivariable regression analysis. Of the 117 referrals who became donors, 27 (23.1%) arrested more than 1 h after WLST. Longer agonal-phase times were associated with greater donor instability, but surprisingly neither agonal-phase instability nor its duration influenced transplant outcome. In contrast, 3- and 12-month eGFR in the 190 transplanted kidneys was influenced independently by donor age, and 3-month eGFR by cold ischemic time. DCD kidney numbers are increased by 30%, without compromising transplant outcome, by lengthening the minimum waiting time after WLST from 1 to 4 h.

Electrical and optical spectroscopy for quantitative screening of hepatic steatosis in donor livers

Macro-steatosis in deceased donor livers is increasingly prevalent and is associated with poor or non-function of the liver upon reperfusion. Current assessment of the extent of steatosis depends upon the macroscopic assessment of the liver by the surgeon and histological examination, if available. In this paper we demonstrate electrical and optical spectroscopy techniques which quantitatively characterize fatty infiltration in liver tissue. Optical spectroscopy showed a correlation coefficient of 0.85 in humans when referenced to clinical hematoxylin and eosin (H&E) sections in 20 human samples. With further development, an optical probe may provide a comprehensive measure of steatosis across the liver at the time of procurement.

Cold machine perfusion versus static cold storage of kidneys donated after cardiac death: a UK multicenter randomized controlled trial

One third of deceased donor kidneys for transplantation in the UK are donated following cardiac death (DCD). Such kidneys have a high rate of delayed graft function (DGF) following transplantation. We conducted a multicenter, randomized controlled trial to determine whether kidney preservation using cold, pulsatile machine perfusion (MP) was superior to simple cold storage (CS) for DCD kidneys. One kidney from each DCD donor was randomly allocated to CS, the other to MP. A sequential trial design was used with the primary endpoint being DGF, defined as the necessity for dialysis within the first 7 days following transplant. The trial was stopped when data were available for 45 pairs of kidneys. There was no difference in the incidence of DGF between kidneys assigned to MP or CS (58% vs. 56%, respectively), in the context of an asystolic period of 15 min and median cold ischemic times of 13.9 h for MP and 14.3 h for CS kidneys. Renal function at 3 and 12 months was similar between groups, as was graft and patient survival. For kidneys from controlled DCD donors (with mean cold ischemic times around 14 h), MP offers no advantage over CS, which is cheaper and more straightforward.

Donor kidney disease and transplant outcome for kidneys donated after cardiac death

Background

Although outcomes of kidney transplants following donation after cardiac death (DCD) and donation after brainstem death (DBD) are similar, generally only optimal younger DCD donors are considered. This study examined the impact of pre-existing donor kidney disease on the outcome of DCD transplants.

Methods

This retrospective study compared the outcome of all DCD kidney transplants performed during 1996–2006 with contemporaneous kidney transplants from DBD donors. Implantation biopsies were scored for glomerular, tubular, parenchymal and vascular disease (global histology score). There were 104 DCD and 104 DBD kidney transplants.

Results

Delayed graft function (DGF) occurred more frequently in DCD than DBD kidneys (64·4 versus 28·8 per cent; P < 0·001). Long-term graft outcome was similar. The only donor factor that influenced outcome was baseline kidney disease, which was similar in both groups, even though DCD donors were younger, with a higher predonation estimated glomerular filtration rate. The global histology score predicted DGF (odds ratio 1·85 per unit; P = 0·006) and graft failure (relative risk 1·55 per unit; P = 0·001), although there was no difference for DCD and DBD kidneys.

Conclusion

Transplant outcomes for DCD and DBD kidneys are comparable. Baseline donor kidney disease influences DGF and graft survival but the impact is no greater for DCD kidneys.

Selective use of ultrasonographic vascular mapping in the assessment of patients before haemodialysis access surgery

Background

Use of routine preoperative ultrasonography to determine the optimum site for haemodialysis access surgery increases the number of distal arteriovenous fistulas formed and improves overall patency rates. Nevertheless its use in all patients is time consuming and costly. This study examined whether clinical parameters could be used to determine the requirement for preoperative ultrasonography.

Methods

Between March 2002 and October 2003, 145 consecutive patients were reviewed in the vascular access clinic. Patients were first assessed clinically, a site for vascular access surgery was proposed, and the need for radiological mapping studies recorded. A second, blinded, clinician determined the site for vascular access surgery using ultrasonography. The correlation between clinical and ultrasonographic findings was then examined.

Results

Ultrasonography was considered unnecessary using clinical criteria in 106 patients. Subsequent ultrasonographic mapping altered the management of only one patient. In contrast, the management of 18 of the 39 patients in whom ultrasonography was thought necessary was influenced by radiological imaging. A 1-year primary patency rate of 77·0 per cent was achieved following vascular access surgery on the study population.

Conclusion

Clinical parameters could be used to determine the need for preoperative vascular ultrasonographic mapping; imaging was not required in the majority of patients.

HER2 and COX2 expression in human prostate cancer

COX2 and HER2 expression are associated with a poor prognosis in prostate cancer and HER2 has been linked to COX2 expression in colorectal cancer. The association between COX2 and HER2 expression was investigated in 117 patients with prostate cancer (89) or Benign prostatic hyperplasia (BPH) (28). Tissue was analysed for HER2 amplification by fluorescent in situ hybridisation, and HER2 and COX2 protein expression by immunohistochemistry (IHC). All tumours analysed expressed COX2 at a significantly higher level than BPH tissue (P=0.041). Only low levels of HER2 gene amplification (8%, 7/89) and HER2 protein expression (12%, 11/89) were observed. HER2 protein expression was rarely observed and did not correlate with HER2 amplification or COX2 expression. Although HER2 does not drive COX2 expression in prostate cancer, this study identified high levels of COX2 expressed in locally advanced prostate cancer, suggesting COX2 could be a potential therapeutic target. COX2 inhibitors are currently being used in clinical trials for the treatment of other tumour types.

Uptake of lead by inhalation of motor exhaust

Tetraethyl lead was labelled with 203 Pb, added to petrol, and burnt in an engine. The exhaust aerosol was inhaled by volunteers, usually after it had been stored in a box, but in a few experiments directly, a few metres downwind of the engine. The percentage deposition in the lung, uptake to blood and excretion of the labelled lead were measured. The percentage deposition in the lung depended on the length of the respiratory cycle. For a 4 s cycle (15 breaths/min) the deposition was 35 ± 2 (s. e.)%. Most of the 203 Pb was removed from the lung with a half life of about 6 h. About half of the amount deposited in the lung was in the blood at 50 h after inhalation. A similar fraction was in the blood at the same time after injection of 203 PbCl 2 in saline solution. From this and other evidence it is deduced that most of the 203 Pb passed from the lung to the blood plasma. About half was removed to bone and other tissues, and half became attached to red cells. From about 72 h onwards, the amount of 203 Pb in blood declined with a mean biological half life of 16 d. Assuming that the same half life applies beyond the period for which measurements were made, the results can be used to predict that con­tinuous (24 h/d) exposure to 1 μ g/m 3 of exhaust lead over a period of months will given an average contribution of about 1 μg/l00 ml to blood lead. Results of other work on experimental and industrial exposure of persons to lead in air appear consistent with this.

Uptake of inhaled lead from motor exhaust

Images

Deposition in the lung and uptake to blood of motor exhaust labelled with 203Pb

Inhalation of airborne lead from automobile exhaust is a significant source of intake. In these experiments a radioactive isotope of lead was used to label tetraethyl lead consumed in petrol engines. The resulting aerosols were inhaled by human volunteers to determine the percentage deposition in the lung, the pattern of removal from the lung and the resulting levels in the blood and excreta. Deposition in lung was shown to depend on particle size, varying from 40% for fresh, highly diluted aerosols to 14% for mature, aggregated aerosols, at a breathing rate of 15 breaths per minute. For aggregated aerosols the influence of rate of breathing, tidal volume and reserve volume was investigated. Uptake from the lung was rapid (T 1/2=6.6 h) and virtually complete with little, if any, ciliary clearance. Fifty per cent of the labelled lead remained in the blood, the concentration peaking after 2 days and subsequently declining exponentially (T 1/2 = 16 d). Total excretion was of the order of 1% of the intake per day up to 15 days.