Microarray analyses demonstrate the involvement of type i interferons in psoriasiform pathology development in D6-deficient mice

The inflammatory response is normally limited by mechanisms regulating its resolution. In the absence of resolution, inflammatory pathologies can emerge, resulting in substantial morbidity and mortality. We have been studying the D6 chemokine scavenging receptor, which played an indispensable role in the resolution phase of inflammatory responses and does so by facilitating removal of inflammatory CC chemokines. In D6-deficient mice, otherwise innocuous cutaneous inflammatory stimuli induce a grossly exaggerated inflammatory response that bears many similarities to human psoriasis. In the present study, we have used transcriptomic approaches to define the molecular make up of this response. The data presented highlight potential roles for a number of cytokines in initiating and maintaining the psoriasis-like pathology. Most compellingly, we provide data indicating a key role for the type I interferon pathway in the emergence of this pathology. Neutralizing antibodies to type I interferons are able to ameliorate the psoriasis-like pathology, confirming a role in its development. Comparison of transcriptional data generated from this mouse model with equivalent data obtained from human psoriasis further demonstrates the strong similarities between the experimental and clinical systems. As such, the transcriptional data obtained in this preclinical model provide insights into the cytokine network active in exaggerated inflammatory responses and offer an excellent tool to evaluate the efficacy of compounds designed to therapeutically interfere with inflammatory processes

D6: the 'crowd controller’ at the immune gateway

The chemokine-scavenging receptor, D6, is reported to regulate resolution of inflammatory responses. However, recent data also point to an unanticipated role for D6 in coordinating innate and adaptive immune responses. Here, we propose that D6 is essential for preventing inflammatory leukocyte association with lymphatic vasculature. In the absence of D6, inappropriate inflammatory leukocyte accumulation around lymphatic endothelium congests the lymphatic system, impairing fluid and cellular flow from inflamed sites to lymph nodes and reducing efficiency of antigen presentation. Thus, the inability of D6-deficient mice to resolve inflammation may be a byproduct of impaired fluid drainage from inflamed sites and thus we provide a model unifying D6 function in innate and adaptive immune responses

Mast cells reside in myometrium and cervix, but are dispensable in mice for successful pregnancy and labor

Parturition is associated with myometrial and cervical inflammation. The causes and consequences of this inflammatory response are not clear. Mast cells (MCs) are important inducers of allergic and non-allergic inflammation, and their secreted products can induce myometrial contractions. Thus, mast cell activation has been hypothesized to have a role in initiating labor and/or driving labor-associated inflammation. We report that small numbers of MCs expressing chymase and tryptase are present in the myometrium and cervix of pregnant women. Labor did not lead to any change in mast cell abundance in these tissues, but was associated with reduced expression of the mast-cell regulator FcɛR1A, indicative of a change in mast cell properties. This coincided with contraction-dependent myocyte production of interleukin-10 (IL-10), a known suppressor of FcɛR1A expression. MCs were also found in the uterine horn and cervical region of pregnant C57BL/6 mice, increasing in number in the cervix, but not the myometrium, with labor. As expected, these cells were absent from mast-cell-deficient Kit(W-sh) mice. Nonetheless, pregnant Kit(W-sh) mice showed no defects in the timing of labor induction or in the upregulation of leukocyte markers during labor. Thus, MCs are present in the uterus and cervix of humans and mice, and our mouse studies suggest that they do not have a vital role in the induction of labor, or in the promotion of labor-associated inflammation

P014 Identification of Crohn’s Disease Immunopathotypes

Background: Crohn’s disease (CD) is a chronic inflammatory gastrointestinal condition, with globally increasing incidence. Patients with CD suffer from a loss of tolerance towards their commensal microbiota causing an aberrant immune response, occurring in a protracted relapse and remission cycle. Although a variety of frontline therapies is currently available, including targeted therapies such as biologic drugs, 30–40% of CD patients still require surgery to manage the disease. At present, the immunobiology of CD is not fully understood. However, differences in immune responses between patients might play an important role in diverse treatment responses. The aim of this study was to identify differences in peripheral and local immune responses of CD to understand differences in disease behaviour and treatment outcome. Methods: Peripheral blood mononuclear cells and plasma were isolated from whole blood of a cross-sectional CD patient cohort (nCD = 12) and normal controls (NC, nNC = 28). Flow cytometry analysis and multiplex assays were used to quantify immune cell populations and cytokine levels, respectively. The local immune response was analysed by bulk RNA sequencing of mucosal colonic biopsies either from inflamed CD or normal tissue. Gene signatures were then followed up by validation in publicly deposited gene expression datasets (nCD = 36, nNC = 24), and by measurement of specific proteins using our archived samples. Results: Peripheral immunophenotyping of the initial cross-sectional study displayed three different types of CD patients, characterised by either a decrease in leukocyte populations, an increase of cytokines, or a change in both. Analysis of the RNAseq data derived from colonic biopsies revealed four distinct clusters in genes associated with the immune response in CD patients. Further pathway analysis showed one cluster with an enriched B cell signature and another cluster with an elevated macrophage and neutrophil response. We utilised publicly available gene expression datasets to validate these signatures in a larger cohort and identified a selection of patients with an up-regulated pro-inflammatory macrophage response. Using correlation analysis, we suggest an immunopathotype with increased macrophage activation which is potentially associated with a more severe form of the disease. Conclusion: We have identified distinct immunopathotypes in both the peripheral and local immune response of CD patients. Further investigation will correlate these distinct immune responses in CD with clinical parameters, to understand associations between diverse treatment responses and disease behaviours

An analysis of the function and expression of D6 on lymphatic endothelial cells

The mechanisms by which CCR7 ligands are selectively presented on lymphatic endothelium in the presence of inflammatory chemokines are poorly understood. The chemokine-scavenging receptor D6 is expressed on lymphatic endothelial cells (LEC) and contributes to selective presentation of CCR7 ligands by suppressing inflammatory chemokine binding to LEC surfaces. Here we show that, as well as preventing inappropriate inflammatory cell attachment to LECs, D6 is specifically involved in regulating the ability of LEC to discriminate between mature and immature DCs. D6 overexpression reduces immature DC adhesion to LECs, whilst D6 knockdown increases adhesion of immature DCs that displace mature DCs. LEC D6 expression is regulatable by growth factors, cytokines and tumor microenvironments. In particular IL-6 and IFNγ are potent inducers indicating a preferential role for D6 in inflamed contexts. Expression of the vIL-6 homologue from Kaposi's Sarcoma-Associated Herpesvirus (KSHV) is also sufficient to induce significant D6 up-regulation both in vitro and in vivo and KS, as well as Primary Effusion Lymphoma cells, demonstrate high levels of D6 expression. We therefore propose that D6, which is upregulated in both inflammatory and tumor contexts, is an essential regulator of inflammatory leukocyte interactions with LECs and is required for immature/mature DC discrimination by LECs