CD31 exhibits multiple roles in regulating T lymphocyte trafficking in vivo

CD31 orchestrates metabolic regulation in autophagy pathways of rheumatoid arthritis

Synovitis is characterized by a distinctmetabolic profile featuring the accumulation of lactate, a byproduct of cellular metabolism within inflamed joints. This study reveals that the activation of the CD31 signal by lactate instigates a metabolic shift, specifically initiating endothelial cell autophagy. This adaptive process plays a pivotal role in fulfilling the augmented energy and biomolecule demands associated with the formation of new blood vessels in the synovium of Rheumatoid Arthritis (RA). Additionally, the amino acid substitutions in the CD31 cytoplasmic tail at the Y663F and Y686F sites of the immunoreceptor tyrosine-based inhibitory motifs (ITIM) alleviate RA. Mechanistically, this results in the downregulation of glycolysis and autophagy pathways. These findings significantly advance our understanding of potential therapeutic strategies for modulating these processes in synovitis and, potentially, other autoimmune diseases.

Distinct leukocyte populations and cytokine secretion profiles define tumoral and peritumoral areas in renal cell carcinoma

Renal cell carcinoma (RCC) is a common malignancy frequently diagnosed at the metastatic stage. We performed a comprehensive analysis of the tumor immune microenvironment (TIME) in RCC patients, including the peritumoral tissue microenvironment, to characterize the phenotypic patterns and functional characteristics of infiltrating immune cells. T cells from various compartments (peripheral blood, tumor, peritumoral area, and adjacent healthy renal tissue) were assessed using flow cytometry and Luminex analyses, both before and after T cell-specific stimulation, to evaluate activation status and migratory potential. Our findings demonstrated that tumor-infiltrating lymphocytes (TILs) exhibited heightened cytokine production compared to peritumoral T cells (pTILs), acting as the primary source of cytotoxic markers (IFN-γ, granzyme B, and FasL). CD8+ T cells primarily employed Fas Ligand for cytotoxicity, while CD4+ T cells relied on CD107a. In addition, a statistically significant negative correlation between patient mortality and the presence of CD4+CD107+ pTILs was demonstrated. The engagement with the PD-1/PD-L1 pathway was also more evident in CD4+ and CD8+ pTILs as opposed to TILs. PD-L1 expression in the non-leukocyte fraction of the tumor tissue was relatively lower than in their leukocytic counterparts and upon stimulation, peripheral blood T cells displayed much stronger responses to stimulation than TILs and pTILs. Our results suggest that tumor and peritumoral T cells exhibit limited responsiveness to additional activation signals, while peripheral T cells retain their capacity to respond to stimulatory signals.

CD31 as a probable responding and gate-keeping protein of the blood-brain barrier and the risk of Alzheimer's disease

Several studies have shown that an abnormal vascular-immunity link could increase Alzheimer's disease (AD) risk; however, the mechanism is unclear. CD31, also named platelet endothelial cell adhesion molecule (PECAM), is a surface membrane protein of both endothelial and immune cells and plays important roles in the interaction between the vascular and immune systems. In this review, we focus on research regarding CD31 biological actions in the pathological process that may contribute to AD based on the following rationales. First, endothelial, leukocyte and soluble forms of CD31 play multi-roles in regulating transendothelial migration, increasing blood-brain barrier (BBB) permeability and resulting in neuroinflammation. Second, CD31 expressed by endothelial and immune cells dynamically modulates numbers of signaling pathways, including Src family kinases, selected G proteins, and β-catenin which in turn affect cell-matrix and cell-cell attachment, activation, permeability, survival, and ultimately neuronal cell injury. In endothelia and immune cells, these diverse CD31-mediated pathways act as a critical regulator in the immunity-endothelia-brain axis, thereby mediating AD pathogenesis in ApoE4 carriers, which is the major genetic risk factor for AD. This evidence suggests a novel mechanism and potential drug target for CD31 in the background of genetic vulnerabilities and peripheral inflammation for AD development and progression.

Effect of changes in lymphocyte subsets at diagnosis in acute myeloid leukemia on prognosis: association with complete remission rates and relapse free survivals

We prospectively investigated whether the characteristics of lymphocyte subsets at diagnosis in acute myeloid leukemia (AML) patients are different from healthy controls and affect treatment outcomes. A total of 91 AML patients classified into 3 genetic risk subgroups (favorable/intermediate/poor) according to 2022 NCCN guidelines were enrolled. We measured lymphocyte subsets by flow cytometry with peripheral blood samples at diagnosis and compared results with healthy controls. Influences of lymphocyte subsets on complete remission (CR) rates and survivals were also evaluated. AML patients had significantly lower numbers and proportions of CD56dimCD16+ natural killer (NK) cells, central memory T cells, and regulatory T cells than healthy controls. Higher proportion of helper/inducer T cells, CD4+CD31+ naïve T cells, and decreased proportion of NK cells significantly increased CR rates in 65 non-promyelocytic leukemia patients (P = 0.034, 0.027, and 0.019, respectively), and it was also significant in multivariable analysis with age/risk adjusted (P = 0.014, 0.016, and 0.045, respectively). NK cells < 4.8% of lymphocytes demonstrated significantly shorter relapse free survivals (RFS) in both univariate and multivariate analyses with risk adjusted (P = 0.006 and 0.037, respectively). AML patients showed significant lower numbers of CD56dimCD16+ NK cells, central memory T cells, and regulatory T cells than healthy controls at diagnosis. Higher proportion of helper/inducer T cells and CD4+CD31+ naïve T cells and decreased proportion of NK cells at diagnosis were independent factor of increasing probability of CR, and proportion of NK cells < 4.8% at diagnosis had adverse impact in RFS.

Age-dependent transcriptional alterations in cardiac endothelial cells

Aging is a significant risk factor for cardiovascular disease. Despite the fact that endothelial cells play critical roles in cardiovascular function and disease, the molecular impact of aging on this cell population in many organ systems remains unknown. In this study, we sought to determine age-associated transcriptional alterations in cardiac endothelial cells. Highly enriched populations of endothelial cells (ECs) isolated from the heart, brain, and kidney of young (3 mo) and aged (24 mo) C57/BL6 mice were profiled for RNA expression via bulk RNA sequencing. Approximately 700 cardiac endothelial transcripts significantly differ by age. Gene set enrichment analysis indicated similar patterns for cellular pathway perturbations. Receptor-ligand comparisons indicated parallel alterations in age-affected circulating factors and cardiac endothelial-expressed receptors. Gene and pathway enrichment analyses show that age-related transcriptional response of cardiac endothelial cells is distinct from that of endothelial cells derived from the brain or kidney vascular bed. Furthermore, single-cell analysis identified nine distinct EC subtypes and shows that the Apelin Receptor-enriched subtype is reduced with age in mouse heart. Finally, we identify age-dysregulated genes in specific aged cardiac endothelial subtypes.

Characterization of CD31 expression in CD4+ and CD8+T cell subpopulations in chronic untreated HIV infection

BACKGROUND

The platelet endothelial cell adhesion molecule-1 (PECAM-1) or CD31 has been involved in regulation of T-cell tolerance, activation, survival and homing in mice cells. However, there is limited knowledge about the expression pattern and role of this molecule in human T cells, particularly in conditions of chronic immune activation.

OBJECTIVES

We explored CD31 expression in T cell differentiation subsets of individuals with untreated HIV infection and in non-HIV-infected controls. We also assessed phenotypic differences between CD31+ and CD31- subsets in memory and terminally differentiated (TEMRA) CD4+ and CD8 + T cells.

METHODS

Forty-one individuals with untreated HIV infection and 34 non-HIV-infected controls were included in the study. We compared the expression of CD31 in CD4+ and CD8 + T cells across stages of differentiation in the two study groups by flow cytometry. We also analyzed the expression of CD57 (a marker of senescence), Ki67 (a marker of cycling cells), PD-1 (a marker of exhaustion), and CD38/HLA-DR (a marker of immune activation) on memory and TEMRA CD31+ and CD31- T cells.

RESULTS

CD31 expression was significantly higher in CD8 + T cells than in CD4 + T cells, measured as frequency, absolute numbers and median fluorescence intensity (MFI), in both study groups (p < 0.0001 in all cases). Intermediate differentiation subsets of CD4+ and CD8 + T cells expressed higher levels of CD31 in the context of HIV infection (p < 0.001 in all cases). CD31 expression frequency decreased with cellular differentiation of CD4+ and CD8 + T cells in both groups, but this decrease was steeper in individuals without HIV infection (CD4+: p < 0.001 and CD8+: p < 0.0001). As expected, memory and TEMRA CD4+ and CD8 + T cells expressed significantly higher levels of CD57, PD-1, Ki67 and CD38/HLA-DR in HIV-infected compared to non-HIV-infected individuals (p < 0.01 in all cases). CD31 expression was associated with lower activation of memory (but not TEMRA) CD4 + T cells in non-HIV-infected persons, an effect not observed in the HIV-infected group. CD31 expression on memory CD8 + T cells of HIV-infected individuals was associated higher levels of PD-1 (p = 0.0019) and CD38/HLADR (p = 0.0345), and higher PD-1 expression on CD8 + TEMRA (p = 0.0024), an effect not observed in non-HIV-infected individuals.

CONCLUSION

In the context of HIV-associated chronic immune activation, specifically on memory CD8 + T cells, CD31 expression was associated with higher PD-1 and CD38/HLA-DR co-expression, suggesting that CD31 expression may result from an insufficient attempt to contain T cell exhaustion and activation. CD31-targeted therapies may contribute to modulate these cellular responses.

Preservation of microvascular barrier function requires CD31 receptor-induced metabolic reprogramming

Endothelial barrier (EB) breaching is a frequent event during inflammation, and it is followed by the rapid recovery of microvascular integrity. The molecular mechanisms of EB recovery are poorly understood. Triggering of MHC molecules by migrating T-cells is a minimal signal capable of inducing endothelial contraction and transient microvascular leakage. Using this model, we show that EB recovery requires a CD31 receptor-induced, robust glycolytic response sustaining junction re-annealing. Mechanistically, this response involves src-homology phosphatase activation leading to Akt-mediated nuclear exclusion of FoxO1 and concomitant β-catenin translocation to the nucleus, collectively leading to cMyc transcription. CD31 signals also sustain mitochondrial respiration, however this pathway does not contribute to junction remodeling. We further show that pathologic microvascular leakage in CD31-deficient mice can be corrected by enhancing the glycolytic flux via pharmacological Akt or AMPK activation, thus providing a molecular platform for the therapeutic control of EB response.

Loss of BAP1 expression is associated with an immunosuppressive microenvironment in uveal melanoma, with implications for immunotherapy development

Immunotherapy using immune checkpoint inhibitors (ICIs) induces durable responses in many metastatic cancers. Metastatic uveal melanoma (mUM), typically occurring in the liver, is one of the most refractory tumours to ICIs and has dismal outcomes. Monosomy 3 (M3), polysomy 8q, and BAP1 loss in primary uveal melanoma (pUM) are associated with poor prognoses. The presence of tumour-infiltrating lymphocytes (TILs) within pUM and surrounding mUM - and some evidence of clinical responses to adoptive TIL transfer - strongly suggests that UMs are indeed immunogenic despite their low mutational burden. The mechanisms that suppress TILs in pUM and mUM are unknown. We show that BAP1 loss is correlated with upregulation of several genes associated with suppressive immune responses, some of which build an immune suppressive axis, including HLA-DR, CD38, and CD74. Further, single-cell analysis of pUM by mass cytometry confirmed the expression of these and other markers revealing important functions of infiltrating immune cells in UM, most being regulatory CD8+ T lymphocytes and tumour-associated macrophages (TAMs). Transcriptomic analysis of hepatic mUM revealed similar immune profiles to pUM with BAP1 loss, including the expression of IDO1. At the protein level, we observed TAMs and TILs entrapped within peritumoural fibrotic areas surrounding mUM, with increased expression of IDO1, PD-L1, and β-catenin (CTNNB1), suggesting tumour-driven immune exclusion and hence the immunotherapy resistance. These findings aid the understanding of how the immune response is organised in BAP1 - mUM, which will further enable functional validation of detected biomarkers and the development of focused immunotherapeutic approaches. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

NK and T cells with a cytotoxic/migratory phenotype accumulate in peritumoral tissue of patients with clear cell renal carcinoma

OBJECTIVES

Renal cell carcinoma (RCC) is the most lethal urologic malignancy with increasing incidence worldwide. The conventional treatment strategies for advanced or recurrent RCC are not efficient and show considerable toxicities. Adoptive cell transfer (ACT) has become a promising treatment option for multiple cancers, particularly in combination with other therapeutic approaches. ACT often utilizes extensively in vitro expanded tumor-infiltrating lymphocytes (TILs). However, TILs are a very heterogeneous mix of cell populations and only those populations that have a cytotoxic and migratory potential are thought to deliver a therapeutic impact in ACT. The identification and localization of these therapeutically potent populations are therefore needed.

METHODS AND MATERIALS

A total number of 57 tissue samples from 19 RCC patients who underwent radical nephrectomy was analyzed. The tissue samples were obtained from the tumor, peritumoral tissue, and the adjacent healthy renal tissue. The tissues were sliced, enzymatically dissociated into single cell suspensions and the obtained cells further analyzed by flow cytometry for the expression of markers of lymphocyte cytotoxicity - TRAIL and FasL, and a surrogate marker of lymphocyte migratory activity - PECAM-1. The analyzed data were next correlated with the clinical and histopathological data.

RESULTS

Non-clear cell RCC (non-ccRCC) tumors showed a significantly decreased tumor infiltration with TRAIL⁺FasL⁺ NK cells but elevated infiltration with FasL⁺PECAM-1⁺ T cells as compared with clear cell RCC (ccRCC) tumors. Further analyses revealed that the peritumoral tissue of ccRCC patients is a reservoir of TRAIL⁺FasL⁺, TRAIL⁺PECAM-1⁺, or FasL⁺PECAM-1⁺ NK and T cells.

CONCLUSIONS

The cytotoxic/migratory lymphocytes were identified in tumors of ccRCC patients. These lymphocytes became excluded from the tumor and accumulated in the patient's peritumoral tissue.

Neonatal influenza-specific effector CTLs retain elevated CD31 levels at the site of infection and have decreased IFN-γ production

The underlying mechanisms that regulate neonatal immune suppression are poorly characterized. CD31 (PECAM1) is highly expressed on neonatal lymphocytes and is a known modulator of TCR signaling. To further characterize the role of CD31 in the neonatal CTL response, 3-d and 7-d-old murine neonates were infected with influenza virus and compared to adults. The majority of the pulmonary viral-specific CTLs in the 3-d-old murine neonate retain CD31 expression, whereas adult CTLs have decreased CD31 expression. In addition, CD31⁺ neonatal viral-specific CTLs demonstrate decreased IFN-γ production, decreased proliferative capacity, and increased likelihood of death. At the peak of infection, sorted neonatal effector CTLs continue to transcribe CD31, indicating a developmental regulation of expression. To explore potential mechanisms for this reduced function, we compared the expression of the transcription factors Eomesodermin (Eomes) and T-bet; there was a significant increase in Eomes paired with a reduction in T-bet in CD31⁺ neonatal effector CTLs in the lung. Furthermore, in vitro stimulated neonatal CTLs significantly reduce IFN-γ production upon CD31 signaling. Altogether, these data indicate that neonatal CTLs may retain elevated levels of CD31 to maintain peripheral T cell suppression during the bridge to ex utero life.

Activated dendritic cells delivered in tissue compatible biomatrices induce in-situ anti-tumor CTL responses leading to tumor regression

Dendritic cell (DC) based anti-cancer immunotherapy is well tolerated in patients with advanced cancers. However, the clinical responses seen after adoptive DC therapy have been suboptimal. Several factors including scarce DC numbers in tumors and immunosuppressive tumor microenvironments contribute to the inefficacy of DCs as cellular vaccines. Hence DC based vaccines can benefit from novel methods of cell delivery that would prevent the direct exposure of immune cells to suppressive tumor microenvironments. Here we evaluated the ability of DCs harbored in biocompatible scaffolds (referred to as biomatrix entrapped DCs; beDCs) in activating specific anti-tumor immune responses against primary and post-surgery secondary tumors. Using a preclinical cervical cancer and a melanoma model in mice, we show that single treatment of primary and post-surgery secondary tumors using beDCs resulted in significant tumor growth retardation while multiple inoculations were required to achieve a significant anti-tumor effect when DCs were given in free form. Additionally, we found that, compared to the tumor specific E6/E7 peptide vaccine, total tumor lysate induced higher expression of CD80 and CD40 on DCs that induced increased levels of IFNγ production upon interaction with host lymphocytes. Remarkably, a strong immunocyte infiltration into the host-implanted DC-scaffold was observed. Importantly, the host-implanted beDCs induced the anti-tumor immune responses in the absence of any stromal cell support, and the biomatrix structure was eventually absorbed into the surrounding host tissue. Collectively, these data indicate that the scaffold-based DC delivery may provide an efficient and safe way of delivering cell-based vaccines for treatment of primary and post-surgery secondary tumors.

Antigen Presentation by Vascular Cells

Antigen presentation by cells of the vessel wall may initiate rapid and localized memory immune responses in peripheral tissues. Peptide antigens displayed on major histocompatibility complex (MHC) molecules on the surface of endothelial cells (ECs) can be recognized by T cell receptors on circulating effector memory T cells (T_EM), triggering both transendothelial migration and activation. The array of co-stimulatory receptors, adhesion molecules, and cytokines expressed by ECs serves to modulate T cell activation responses. While the effects of these interactions vary among species, vascular beds, and vascular segments within the same tissue, they are capable of triggering allograft rejection without direct involvement of professional antigen-presenting cells and may play a similar role in host defense against infections and in autoimmunity. Once across the endothelium, extravasating T_EM then contact mural cells of the vessel wall, including pericytes or vascular smooth muscle cells, which may also present antigens and provide signals that further regulate T cell responses. Collectively, these interactions provide an unexplored opportunity in which targeting of vascular cells can be used to modulate immune responses. In organ transplantation, targeting ECs with siRNA to reduce expression of MHC molecules may additionally mitigate perioperative injuries by preformed alloantibodies, further reducing the risk of graft rejection. Similarly, genetic manipulation of vascular cells to minimize antigen-dependent responses can be used to increase perfusion of tissue engineered organs without triggering rejection.

Expression of a Chimeric Antigen Receptor Specific for Donor HLA Class I Enhances the Potency of Human Regulatory T Cells in Preventing Human Skin Transplant Rejection

Regulatory T cell (Treg) therapy using recipient-derived Tregs expanded ex vivo is currently being investigated clinically by us and others as a means of reducing allograft rejection following organ transplantation. Data from animal models has demonstrated that adoptive transfer of allospecific Tregs offers greater protection from graft rejection compared to polyclonal Tregs. Chimeric antigen receptors (CAR) are clinically translatable synthetic fusion proteins that can redirect the specificity of T cells toward designated antigens. We used CAR technology to redirect human polyclonal Tregs toward donor-MHC class I molecules, which are ubiquitously expressed in allografts. Two novel HLA-A2-specific CARs were engineered: one comprising a CD28-CD3ζ signaling domain (CAR) and one lacking an intracellular signaling domain (ΔCAR). CAR Tregs were specifically activated and significantly more suppressive than polyclonal or ΔCAR Tregs in the presence of HLA-A2, without eliciting cytotoxic activity. Furthermore, CAR and ΔCAR Tregs preferentially transmigrated across HLA-A2-expressing endothelial cell monolayers. In a human skin xenograft transplant model, adoptive transfer of CAR Tregs alleviated the alloimmune-mediated skin injury caused by transferring allogeneic peripheral blood mononuclear cells more effectively than polyclonal Tregs. Our results demonstrated that the use of CAR technology is a clinically applicable refinement of Treg therapy for organ transplantation.

Uterine natural killer cell partnerships in early mouse decidua basalis

The decidua basalis of developing mouse implantation sites is highly enriched in CD45⁺ leukocytes. In intact, syngeneically mated C57BL/6 decidua basalis examined at gestation day 8.5 by whole-mount in situ immunohistochemistry, leukocyte, but not trophoblast, conjugations were reported. Nothing is known regarding time course, frequency, composition, or importance of physiologic decidual CD45⁺ cell pairing. In this study, we confirmed the presence of anti-CD54⁺/anti-CD11a⁺ immune synapses in CD45⁺ decidual cell conjugates and characterized their cellular heterogeneity. Conjugated cell pairs were virtually absent before implantation (virgin and gestation days 3.5 and 4.5), were infrequent at gestation day 5.5, but involved 19% of all CD45⁺ cells by gestation day 8.5, then declined. By gestation day 8.5, almost all CD45⁺ cells coexpressed CD31, and 2 CD45⁺CD31⁺ cells composed most conjugates. Conjugation partners were defined for 2 nonoverlapping uterine natural killer cell subsets (Ly49C/I ⁺/Dolichos biflorus agglutinin lectin^- and Ly49C/I^-/Dolichos biflorus agglutinin lectin⁺). Ly49C/I⁺ uterine natural killer cells were the major subset from before mating up to gestation day 6.5. At gestation day 5.5/6.5, uterine natural killer cell conjugates involving Ly49C/I ⁺ cells were more abundant. By gestation day 8.5/9.5, Dolichos biflorus agglutinin lectin⁺ uterine natural killer cells were the dominant subset with Dolichos biflorus agglutinin lectin⁺/Dolichos biflorus agglutinin lectin⁺ homologous conjugates and Dolichos biflorus agglutinin lectin⁺/Dolichos biflorus agglutinin lectin^- heterologous conjugates dominating uterine natural killer cell pairings. At gestation day 6.5, both Ly49C/I⁺/CD45⁺ and Dolichos biflorus agglutinin lectin⁺/CD45⁺ heterologous conjugate pairs strongly engaged antigen-presenting cells (CD11c⁺, CD68⁺, or major histocompatibility complex class II⁺). By gestation day 8.5, dominant partners of Ly49C/I⁺/CD45⁺ and Dolichos biflorus agglutinin lectin⁺/CD45⁺ heterologous conjugates are T cells (CD8⁺ >CD4⁺). Heterologous conjugates that did not involve uterine natural killer cells occurred but did not suggest antigen presentation to T cells. These data identify gestation day 6.5-8.5 in the pregnant mouse as a critical window for leukocyte interactions that may establish immune regulation within implantation sites.

CD31 signals confer immune privilege to the vascular endothelium

Constitutive resistance to cell death induced by inflammatory stimuli activating the extrinsic pathway of apoptosis is a key feature of vascular endothelial cells (ECs). Although this property is central to the maintenance of the endothelial barrier during inflammation, the molecular mechanisms of EC protection from cell-extrinsic, proapoptotic stimuli have not been investigated. We show that the Ig-family member CD31, which is expressed by endothelial but not epithelial cells, is necessary to prevent EC death induced by TNF-α and cytotoxic T lymphocytes in vitro. Combined quantitative RT-PCR array and biochemical analysis show that, upon the engagement of the TNF receptor with TNF-α on ECs, CD31 becomes activated and, in turn, counteracts the proapoptotic transcriptional program induced by TNF-α via activation of the Erk/Akt pathway. Specifically, Akt activation by CD31 signals prevents the localization of the forkhead transcription factor FoxO3 to the nucleus, thus inhibiting transcription of the proapoptotic genes CD95/Fas and caspase 7 and de-repressing the expression of the antiapoptotic gene cFlar. Both CD31 intracellular immunoreceptor tyrosine-based inhibition motifs are required for its prosurvival function. In vivo, CD31 gene transfer is sufficient to recapitulate the cytoprotective mechanisms in CD31(-) pancreatic β cells, which become resistant to immune-mediated rejection when grafted in fully allogeneic recipients.

Tissue instruction for migration and retention of TRM cells

During infection, a subset of effector T cells seeds the lymphoid and non-lymphoid tissues and gives rise to tissue-resident memory T cells (TRM). Recent findings have provided insight into the molecular and cellular mechanisms underlying tissue instruction of TRM cell homing, as well as the programs involved in their retention and maintenance. We review these findings here, highlighting both common features and distinctions between CD4 TRM and CD8 TRM cells. In this context we examine the role of memory lymphocyte clusters (MLCs), and propose that the MLCs serve as an immediate response center consisting of TRM cells on standby, capable of detecting incoming pathogens and mounting robust local immune responses to contain and limit the spread of infectious agents.

Homeostatic regulation of T cell trafficking by a B cell-derived peptide is impaired in autoimmune and chronic inflammatory disease

During an inflammatory response, lymphocyte recruitment into tissue must be tightly controlled because dysregulated trafficking contributes to the pathogenesis of chronic disease. Here we show that during inflammation and in response to adiponectin, B cells tonically inhibit T cell trafficking by secreting a peptide (PEPITEM) proteolytically derived from 14.3.3.ζδ protein. PEPITEM binds cadherin-15 on endothelial cells, promoting synthesis and release of sphingosine-1 phosphate, which inhibits trafficking of T cells without affecting recruitment of other leukocytes. Expression of adiponectin receptors on B cells and adiponectin induced PEPITEM secretion wanes with age, implying immune senescence of the pathway. Additionally, these changes are evident in individuals with type-1-diabetes or rheumatoid arthritis, and circulating PEPITEM in patient serum is reduced compared to healthy age matched donors. In both diseases, tonic inhibition of T cell trafficking across inflamed endothelium is lost. Importantly, control of patient T cell trafficking is re-established by exogenous PEPITEM. Moreover, in animal models of peritonitis, hepatic I/R injury, Salmonella infection, Uveitis and Sjögren’s Syndrome, PEPITEM could reduce T cell recruitment into inflamed tissues.

Impact of placental growth factor deficiency on early mouse implant site angiogenesis

Effects of placental growth factor (PGF), an angiokine product of fetal trophoblasts and maternal decidual cells, on early decidual angiogenesis are undefined. We used whole-mount immunofluorescence analyses to compare uterus and gestation day 4.5-9.5 mouse implantation sites that differed genetically in fetal or maternal PGF deficiency. Implant site number and embryonic development were similar in Pgf(-/-) and Pgf(+/+) females although Pgf(-/-) lymphatic vessels were anomalous. Correct, fine branching angiogenesis of anti-mesometrial vessels required both conceptus and maternal PGF; correct mesometrial branching angiogenesis depended solely upon conceptus PGF. Thus, PGF is non-redundant for optimizing branching angiogenesis in early decidua.

Bevacizumab plus ipilimumab in patients with metastatic melanoma

Ipilimumab improves survival in advanced melanoma and can induce immune-mediated tumor vasculopathy. Besides promoting angiogenesis, vascular endothelial growth factor (VEGF) suppresses dendritic cell maturation and modulates lymphocyte endothelial trafficking. This study investigated the combination of CTLA4 blockade with ipilimumab and VEGF inhibition with bevacizumab. Patients with metastatic melanoma were treated in four dosing cohorts of ipilimumab (3 or 10 mg/kg) with four doses at 3-week intervals and then every 12 weeks, and bevacizumab (7.5 or 15 mg/kg) every 3 weeks. Forty-six patients were treated. Inflammatory events included giant cell arteritis (n = 1), hepatitis (n = 2), and uveitis (n = 2). On-treatment tumor biopsies revealed activated vessel endothelium with extensive CD8(+) and macrophage cell infiltration. Peripheral blood analyses demonstrated increases in CCR7(+/-)/CD45RO(+) cells and anti-galectin antibodies. Best overall response included 8 partial responses, 22 instances of stable disease, and a disease-control rate of 67.4%. Median survival was 25.1 months. Bevacizumab influences changes in tumor vasculature and immune responses with ipilimumab administration. The combination of bevacizumab and ipilimumab can be safely administered and reveals VEGF-A blockade influences on inflammation, lymphocyte trafficking, and immune regulation. These findings provide a basis for further investigating the dual roles of angiogenic factors in blood vessel formation and immune regulation, as well as future combinations of antiangiogenesis agents and immune checkpoint blockade.

Evaluation of peri-implant mucosa: clinical, histopathological and immunological aspects

OBJECTIVE

The aim was to compare the inflammatory response in peri-implant mucosa between patients with peri-implantitis (PP-group) and patients with healthy peri-implant tissues (HP-group).

MATERIALS AND METHODS

Two fragments of peri-implant mucosa of 18 patients were collected and serial sections were performed for histological and immunohistochemical analysis.

RESULTS

When compared with HP-group, PP-group showed higher immunostained cell density for TGF-β, IL-17 and CD31, beyond greater density of red cells, leukocytes, mast cells chymase (MCC) and mast cell tryptase (MCT). HP-group patients showed higher IL-13 expression and increased amount of collagen fibres when compared with PP-group. In PP-group there was significant positive correlation between MCT density and density of blood vessels immunostained, and between MCC density and density of blood vessels immunostained. There was significant negative correlation between the IL-17 density and collagen percentage.

CONCLUSIONS

This study demonstrated that in patients with peri-implantitis there was higher of TGF-β and IL-17, indicating that these cytokines are directly involved in the inflammatory process. Thus, understanding the influence of cytokines in the peri-implantitis installation, new therapies could be developed in order to inhibit the synthesis of IL-17 and induce synthesis of IL-13 in peri-implant tissue, contributing to increase the longevity of the implant.

An immunologist's guide to CD31 function in T-cells

Although it is expressed by all leukocytes, including T-, B-lymphocytes and dendritic cells, the immunoglobulin-like receptor CD31 is generally regarded by immunologists as a marker of endothelial cell lineage that lacks an established functional role in adaptive immunity. This perception has recently been challenged by studies that reveal a key role for this molecule in the regulation of T-cell homeostasis, effector function and trafficking. The complexity of the biological functions of CD31 results from the integration of its adhesive and signaling functions in both the immune and vascular systems. Signaling by means of CD31 is induced by homophilic engagement during the interactions of immune cells and is mediated by phosphatase recruitment or activation through immunoreceptor tyrosine inhibitory motifs (ITIMs) that are located in its cytoplasmic tail. Loss of CD31 function is associated with excessive immunoreactivity and susceptibility to cytotoxic killing. Here, we discuss recent findings that have brought to light a non-redundant, complex role for this molecule in the regulation of T-cell-mediated immune responses, with large impact on our understanding of immunity in health and disease.

Receptors for non-MHC ligands contribute to uterine natural killer cell activation during pregnancy in mice

INTRODUCTION

Activated uterine natural killer (uNK) cells are abundant in early human and mouse decidual basalis. In mice, distinct uNK cell subsets support early endothelial tip cell induction, the pruning of new vessels and initiation of spiral arterial modification. While genetic studies indicate that NK/uNK cell activation via receptors recognizing Class I MHC-derived peptides promotes human pregnancy, roles for other activation receptors expressed by NK cells, such as the aryl hydrocarbon receptor (AHR) and natural cytotoxicity receptors (NCR) are undefined in human or mouse pregnancies.

METHODS

Expression of AHR and NCR1 (ortholog of human NKp46) by gestation day (gd)10.5 mouse uNK cell subsets was measured by quantitative real-time RT-PCR. Early implantation sites from mice lacking expression of either receptor were examined histologically.

RESULTS

Gd10.5 uNK cell subsets, separated by reactivity to Dolichos biflorus agglutinin lectin, differed in relative transcript abundance for Ahr and Ncr1. Quantitative histology revealed that, in comparison to C57BL/6 controls, implant sites from gd10.5 Ahr(-/-) and gd6.5-12.5 UkCa:B6.Ncr1(Gfp/Gfp) mice had normal uNK cell abundance but the uNK cells were smaller than normal and unable to trigger spiral arterial remodeling. Whole mount immunohistochemistry comparisons of viable, gd6.5-8.5 Ncr1(Gfp/Gfp) and C57BL/6 implant sites revealed deficits in implant site angiogenesis and conceptus growth in Ncr1(Gfp/Gfp).

DISCUSSION

In mice, activation of AHR and of NCR1 by endogenous, as yet undefined ligands, contributes to uNK cell activation/maturation and angiogenic functions during early to mid-gestation pregnancy. MHC-independent activation of uNK cells also likely makes critical contributions to human pregnancy success.