K. Alun Brown

Ligation of the adhesion-GPCR EMR2 regulates human neutrophil function

At present, ~150 different members of the adhesion‐G protein‐coupled receptor (GPCR) family have been identified in metazoans. Surprisingly, very little is known about their function, although they all possess large extracellular domains coupled to a seven‐transmembrane domain, suggesting a potential role in cell adhesion and signaling. Here, we demonstrate how the human‐restricted adhesion‐GPCR, EMR2 (epidermal growth factor‐like module‐containing mucin‐like hormone receptor), regulates neutrophil responses by potentiating the effects of a number of proinflamma‐tory mediators and show that the transmembrane region is critical for adhesion‐GPCR function. Using an anti‐EMR2 antibody, ligation of EMR2 increases neu‐trophil adhesion and migration, and augments superoxide production and proteolytic enzyme degranulation. On neutrophil activation, EMR2 is rapidly translocated to membrane ruffles and the leading edge of the cell. Further supporting the role in neutrophil activation, EMR2 expression on circulating neutrophils is significantly increased in patients with systemic inflammation. These data illustrate a definitive function for a human adhesion‐GPCR within the innate immune system and suggest an important role in potentiating the inflammatory response. Ligation of the adhesion‐GPCR EMR2 regulates human neutrophil function.—Yona S., Lin, H.‐H., Dri, P., Davies, J. Q., Hayhoe, R. P. G., Lewis, S. M., Heinsbroek, S. E. M., Brown, K. A., Perretti, M., Hamann, J., Treacher, D. F., Gordon S., Stacey M. Ligation of the adhesion‐GPCR EMR2 regulates human neutrophil function. FASEB J. 22, 741–751 (2008)

Targeting cytokines as a treatment for patients with sepsis: A lost cause or a strategy still worthy of pursuit?

Despite often knowing the aetiology of sepsis and its clinical course there has not been the anticipated advances in treatment strategies. Cytokines are influential mediators of immune/inflammatory reactions and in patients with sepsis high circulating levels are implicated in the onset and perpetuation of organ failure. Antagonising the activities of pro-inflammatory cytokines enhances survival in animal models of sepsis but, so far, such a therapeutic strategy has not improved patient outcome. This article addresses the questions of why encouraging laboratory findings have failed to be translated into successful treatments of critically ill patients and whether modifying cytokine activity still remains a promising avenue for therapeutic advance in severe sepsis. In pursuing this task we have selected reports that we believe provide an incisive, critical and balanced view of the topic.

Predictive value of cell-surface markers in infections in critically ill patients: protocol for an observational study (ImmuNe FailurE in Critical Therapy (INFECT) Study)

Introduction Critically ill patients are at high risk of nosocomial infections, with between 20% and 40% of patients admitted to the intensive care unit (ICU) acquiring infections. These infections result in increased antibiotic use, and are associated with morbidity and mortality. Although critical illness is classically associated with hyperinflammation, the high rates of nosocomial infection argue for an importance of effect of impaired immunity. Our group recently demonstrated that a combination of 3 measures of immune cell function (namely neutrophil CD88, monocyte HLA-DR and % regulatory T cells) identified a patient population with a 2.4–5-fold greater risk for susceptibility to nosocomial infections. Methods and analysis This is a prospective, observational study to determine whether previously identified markers of susceptibility to nosocomial infection can be validated in a multicentre population, as well as testing several novel markers which may improve the risk of nosocomial infection prediction. Blood samples from critically ill patients (those admitted to the ICU for at least 48 hours and requiring mechanical ventilation alone or support of 2 or more organ systems) are taken and undergo whole blood staining for a range of immune cell surface markers. These samples undergo analysis on a standardised flow cytometry platform. Patients are followed up to determine whether they develop nosocomial infection. Infections need to meet strict prespecified criteria based on international guidelines; where these criteria are not met, an adjudication panel of experienced intensivists is asked to rule on the presence of infection. Secondary outcomes will be death from severe infection (sepsis) and change in organ failure. Ethics and dissemination Ethical approval including the involvement of adults lacking capacity has been obtained from respective English and Scottish Ethics Committees. Results will be disseminated through presentations at scientific meetings and publications in peer-reviewed journals. Trial registration number NCT02186522; Pre-results.

Adhesion of Dendritic Cells to Endothelia

Many of the interdigitating dendritic cells (DC) that reside in lymph nodes arise from the migration of tissue interstitial DC such as Langerhans cells in the skin (1). Although this migration appears to be stimulated by cytokines (2), relatively little is known of the mechanisms underlying the maintenance and expansion of DC in the skin. Langerhans cells are bone-marrow derived (3), and their replacement in the epidermis following transportation of antigen to lymphoid tissue is likely to depend upon the tissue extravasation of circulating DC. Moreover, the continuous passage of DC across blood vessel walls could be responsible for the increase in DC numbers in tumors (4) and sites of chronic inflammation (5,6). Thus, germane to both homeostasis and pathological disturbance would be the interaction of circulating DC with blood vessel walls, and their subsequent entry into the surrounding tissue. The first stage in leukocyte migration across blood vessel walls is binding to vascular endothelium, and for lymphocytes, monocytes and neutrophils this event is governed by adhesion molecules on their surface recognizing corresponding endothelial ligands commonly referred to as vascular adhesion molecules (7). Despite the plethora of information concerning the molecular nature of the attachment of the major leukocyte subpopulations to endothelium, relatively few studies have been undertaken with DC. Understanding the controlling features of DC-endo-thelial cell interaction would be relevant to the clinical application of DC in immunodeficient disorders and malignancies (8,9) and to antagonizing their entry into sites of chronic inflammatory lesions.Many of the interdigitating dendritic cells (DC) that reside in lymph nodes arise from the migration of tissue interstitial DC such as Langerhans cells in the skin (1). Although this migration appears to be stimulated by cytokines (2), relatively little is known of the mechanisms underlying the maintenance and expansion of DC in the skin. Langerhans cells are bone-marrow derived (3), and their replacement in the epidermis following transportation of antigen to lymphoid tissue is likely to depend upon the tissue extravasation of circulating DC. Moreover, the continuous passage of DC across blood vessel walls could be responsible for the increase in DC numbers in tumors (4) and sites of chronic inflammation (5,6). Thus, germane to both homeostasis and pathological disturbance would be the interaction of circulating DC with blood vessel walls, and their subsequent entry into the surrounding tissue. The first stage in leukocyte migration across blood vessel walls is binding to vascular endothelium, and for lymphocytes, monocytes and neutrophils this event is governed by adhesion molecules on their surface recognizing corresponding endothelial ligands commonly referred to as vascular adhesion molecules (7). Despite the plethora of information concerning the molecular nature of the attachment of the major leukocyte subpopulations to endothelium, relatively few studies have been undertaken with DC. Understanding the controlling features of DC-endo-thelial cell interaction would be relevant to the clinical application of DC in immunodeficient disorders and malignancies (8,9) and to antagonizing their entry into sites of chronic inflammatory lesions.

Blood Dendritic Cells are Highly Adherent to Untreated and Cytokine-Treated Cultured Endothelium

Blood dendritic cells are potent stimulators of T cell proliferation1 and their entry into tissues may give rise to the many forms of interdigitating cells such as skin Langerhans cells2. The binding of lymphocytes, monocytes and polymorphonuclear leucocytes to vascular endothelium is dependent in part upon the surface expression of the CD11/CD18 β2 integrin family3, adhesion molecules that are also present on the surface of dendritic cells4. Treatment of endothelium with inflammatory cytokines increases their adhesiveness for leucocytes by inducing or enhancing the expression of other surface adhesion determinants (e. g. ICAM-1) that recognise corresponding receptors (i. e. CDlla) on the leucocytes5.

[111In]oxine labelling of polymorphonuclear leucocytes: doubts concerning elution and effects on cell behaviour

Polymorphonuclear leucocytes (PMN) from normal human subjects were labelled with [111In]oxine (20 muCi 10(8) cells). In the presence of 20% autologous serum (AS), dissociation of 111In from the cells resulted in mean losses of radioactivity of 13% at 3 h and 30% at 24 h. Adherence of 111In-labelled PMN to cultured porcine endothelial monolayers was increased by 40.7 +/- 31.6% after 60 min incubation in 20% AS at 37 degrees C when compared with unlabelled cells. Phagocytosis and intracellular killing of Candida albicans were unaltered by labelling. Elution of 111In from labelled PMN together with enhanced adhesiveness may have important implications for the study of PMN kinetics and the investigation of inflammatory disease.