G. Kaplanski

Interleukin-18 and IL-18 Binding Protein

Interleukin-18 (IL-18) is a member of the IL-1 family of cytokines. Similar to IL-1β, IL-18 is synthesized as an inactive precursor requiring processing by caspase-1 into an active cytokine but unlike IL-1β, the IL-18 precursor is constitutively present in nearly all cells in healthy humans and animals. The activity of IL-18 is balanced by the presence of a high affinity, naturally occurring IL-18 binding protein (IL-18BP). In humans, increased disease severity can be associated with an imbalance of IL-18 to IL-18BP such that the levels of free IL-18 are elevated in the circulation. Increasing number of studies have expanded the role of IL-18 in mediating inflammation in animal models of disease using the IL-18BP, IL-18-deficient mice, neutralization of IL-18, or deficiency in the IL-18 receptor alpha chain. A role for IL-18 has been implicated in several autoimmune diseases, myocardial function, emphysema, metabolic syndromes, psoriasis, inflammatory bowel disease, hemophagocytic syndromes, macrophage activation syndrome, sepsis, and acute kidney injury, although in some models of disease, IL-18 is protective. IL-18 plays a major role in the production of interferon-γ from T-cells and natural killer cells. The IL-18BP has been used safely in humans and clinical trials of IL-18BP as well as neutralizing anti-IL-18 antibodies are in clinical trials. This review updates the biology of IL-18 as well as its role in human disease.

The IL-6-Soluble IL-6Rα Autocrine Loop of Endothelial Activation as an Intermediate Between Acute and Chronic Inflammation: an Experimental Model Involving Thrombin

Thrombin is a procoagulant and proinflammatory molecule in vivo. In vitro, thrombin has been shown to induce endothelial activation, notably IL-8 secretion and adhesion molecule expression. In this study, we showed that thrombin may induce a new cascade leading from acute to chronic inflammation. Thrombin was able to induce the production of both IL-6 and monocyte chemotactic protein-1 (MCP-1) by HUVEC independently of IL-1αβ and TNF-α. Addition of physiological concentrations of exogenous soluble IL-6Rα (sIL-6Rα) to thrombin-activated HUVEC was sufficient to increase the amounts of MCP-1 produced, but not those of IL-8. These effects could be blocked by anti-IL-6 or anti-sIL-6Rα blocking mAb, demonstrating the existence of an autocrine loop of MCP-1 secretion, involving the IL-6/IL-6Rα/gp130 complex on HUVEC. In addition, we identified IL-8-activated neutrophils as a potential source of sIL-6Rα because IL-8 induced IL-6Rα shedding from the neutrophil membranes and increased in parallel sIL-6Rα concentrations in neutrophil supernatants. Furthermore, addition of neutrophils to thrombin-activated HUVEC significantly increased MCP-1 secretion, which could be decreased by blocking IL-6. Thus, thrombin-activated endothelium may induce a cascade of events characterized by IL-8 secretion, neutrophil local infiltration, and the release of IL-6Rα from neutrophil membranes. sIL-6Rα may then complex with IL-6 and increase the amount of MCP-1 produced by thrombin-activated endothelium, favoring monocyte infiltration, and the transformation of acute into chronic inflammation.

IL-18 Induces PD-1–Dependent Immunosuppression in Cancer

Immunosuppressive cytokines subvert innate and adaptive immune responses during cancer progression. The inflammatory cytokine interleukin-18 (IL-18) is known to accumulate in cancer patients, but its pathophysiological role remains unclear. In this study, we show that low levels of circulating IL-18, either exogenous or tumor derived, act to suppress the NK cell arm of tumor immunosurveillance. IL-18 produced by tumor cells promotes the development of NK-controlled metastases in a PD-1-dependent manner. Accordingly, PD-1 is expressed by activated mature NK cells in lymphoid organs of tumor bearers and is upregulated by IL-18. RNAi-mediated knockdown of IL-18 in tumors, or its systemic depletion by IL-18-binding protein, are sufficient to stimulate NK cell-dependent immunosurveillance in various tumor models. Together, these results define IL-18 as an immunosuppressive cytokine in cancer. Our findings suggest novel clinical implementations of anti-PD-1 antibodies in human malignancies that produce IL-18.

Endothelial cell culture: protocol to obtain and cultivate human umbilical endothelial cells.

Endothelial cells play a key role in prominent immunological and pathological processes such as leukocyte trafficking, inflammation, atheroma or cancer cell metastasis. Umbilical veins are probably the most widely used source for human endothelial cells, since they are more easily available than many other vessels, they are free from any pathological process and they are physiologically more relevant than many established cell lines. Here, we describe a standard protocol for preparation, maintenance and quality control of these cells.

Igg4-related Systemic Disease: Features and Treatment Response in a French Cohort

AbstractIgG4-related systemic disease is now recognized as a systemic disease that may affect various organs. The diagnosis is usually made in patients who present with elevated IgG4 in serum and tissue infiltration of diseased organs by numerous IgG4+ plasma cells, in the absence of validated diagnosis criteria. We report the clinical, laboratory, and histologic characteristics of 25 patients from a French nationwide cohort. We also report the treatment outcome and show that despite the efficacy of corticosteroids, a second-line treatment is frequently necessary. The clinical findings in our patients are not different from the results of previous reports from Eastern countries. Our laboratory and histologic findings, however, suggest, at least in some patients, a more broad polyclonal B cell activation than the skewed IgG4 switch previously reported. These observations strongly suggest the implication of a T-cell dependent B-cell polyclonal activation in IgG4-related systemic disease, probably at least in part under the control of T helper follicular cells.

Increased soluble vascular cell adhesion molecule 1 concentrations in patients with primary or systemic lupus erythematosus-related antiphospholipid syndrome Correlations with the severity of thrombosis

OBJECTIVE Recent studies have shown that in vitro endothelial cells are activated by antiphospholipid antibodies and may support leukocyte adhesion. We studied levels of soluble intercellular adhesion molecule 1 (sICAM-1, sCD54), soluble vascular cell adhesion molecule 1 (sVCAM-1, sCD106), and soluble E-selectin (soluble endothelial leukocyte adhesion molecule 1 [sELAM-1, sCD62E]) in sera from patients with primary antiphospholipid syndrome (primary APS), and compared them with those from patients with systemic lupus erythematosus-associated APS (SLE-APS) or pure SLE, as well as with those from 2 control groups composed of healthy volunteers and patients with thrombosis unrelated to autoimmune diseases. METHODS Serum samples from 24 patients with primary APS, 15 patients with SLE-APS, 22 patients with pure SLE, 48 control patients with thrombosis, and 18 healthy volunteers were examined using enzyme-linked immunosorbent assays specific for sICAM-1, sVCAM-1, and sELAM-1. RESULTS Serum levels of sVCAM-1, but not sICAM-1 or sELAM-1, were significantly increased in all patient study groups compared with thrombosis control patients and healthy volunteers, but did not differ between the groups of patients with primary APS, SLE-APS, or pure SLE. Concentrations of sVCAM-1 were significantly higher in primary APS or SLE-APS patients with severe, recurrent thrombosis and were negatively correlated with platelet counts in primary APS patients. In patients with primary APS, sVCAM-1 levels were higher if there was thrombotic kidney involvement and correlated with creatinemia. CONCLUSION Serum sVCAM-1 concentrations are increased in patients with primary APS, especially those with repeated thrombotic events or kidney involvement. These findings suggest that endothelial/ monocyte interaction may be important in the pathogenesis of primary APS.

Interleukin-18, more than a Th1 cytokine.

Together with IL-12 or IL-15, interleukin-18 (IL-18) plays a major role in the production of interferon-γ from T-cells and natural killer cells; thus, IL-18 is considered to have a major role in the Th1 response. However, without IL-12, IL-18 is proinflammatory in an IFNγ independent manner. IL-18 is a member of the IL-1 family of cytokines and similar to IL-1β, the cytokine is synthesized as an inactive precursor requiring processing by caspase-1 into an active cytokine. IL-18 is also present as an integral membrane protein but requires caspase-1 for full activity in order to induce IFNγ. Uniquely, unlike IL-1β, the IL-18 precursor is constitutively present in nearly all cells in healthy humans and animals. The activity of IL-18 is balanced by the presence of a high-affinity, naturally occurring IL-18 binding protein (IL-18BP). In humans, increased disease severity can be associated with an imbalance of IL-18 to IL-18BP such that the levels of free IL-18 are elevated in the circulation. Increasing number of studies have expanded the role of IL-18 in mediating inflammation in animal models of disease using the IL-18BP, IL-18 deficient mice, neutralization of IL-18 or deficiency in the IL-18 receptor alpha chain. A role for IL-18 has been implicated in several autoimmune diseases, myocardial function, emphysema, metabolic syndromes, psoriasis, inflammatory bowel disease, macrophage activation syndrome, sepsis and acute kidney injury, although paradoxically, in some models of disease, IL-18 is protective. The IL-18BP has been used safely in humans and clinical trials of IL-18BP as well as neutralizing anti-IL-18 antibodies are being tested in various diseases.

IL-6 and IL-8 production from cultured human endothelial cells stimulated by infection with Rickettsia conorii via a cell-associated IL-1 alpha-dependent pathway.

Mediterranean spotted fever due to infection by Rickettsia conorii, is characterized by a general vasculitis. This vasculitis is thought to be due to a direct injury to endothelial cells induced by R. conorii. However, production and activity of cytokines on endothelial cells is an important pathway in inflammation, and part of the underlying mechanism of vasculitis. In the present studies, human umbilical vein endothelial cells (HUVEC) infected with R. conorii actively secrete high levels of IL-8 and IL-6 (P < 0.002, and P < 0.03, respectively, compared with uninfected cells). IL-1alpha, IL-1beta, or TNFalpha were not detected in the culture supernates. Nevertheless, IL-6 and IL-8 production was due, in a large part, to a cell-associated form of IL-1 alpha expressed on R. conorii-infected HUVEC, since production of these cytokines was suppressed by 80% (P = 0.0001) and 85% (P < 0.04) by the addition of IL-1 receptor antagonist, or anti-IL-1alpha antibodies (60% inhibition, P < 0.01 and 65% inhibition, P < 0.05, respectively) and IL-1alpha was measured after lysis of R. conorii-infected HUVEC but not in uninfected cells (P < 0.01). Rickettsial lipopolysaccharide does not seem to be involved, since polymyxin B did not reduce cytokine secretion. On the contrary, infection by intracellular R. conorii appears to be necessary to induce IL-1alpha and subsequently IL-8, since formalin-fixed R. conorii did not induce cytokine production. These observations demonstrate that R. conorii-infected HUVEC secrete IL-6 and IL-8 via the induction of cell-associated IL-1alpha, providing a possible mechanism for the vasculitis observed in Mediterranean spotted fever.

Modular transcriptional repertoire analyses of adults with systemic lupus erythematosus reveal distinct type I and type II interferon signatures.

The role of interferon‐α (IFNα) in the pathogenesis of systemic lupus erythematosus (SLE) is strongly supported by gene expression studies. The aim of this study was to improve characterization of the blood IFN signature in adult SLE patients.

Sterile inflammation of endothelial cell-derived apoptotic bodies is mediated by interleukin-1α

Sterile inflammation resulting from cell death is due to the release of cell contents normally inactive and sequestered within the cell; fragments of cell membranes from dying cells also contribute to sterile inflammation. Endothelial cells undergoing stress-induced apoptosis release membrane microparticles, which become vehicles for proinflammatory signals. Here, we show that stress-activated endothelial cells release two distinct populations of particles: One population consists of membrane microparticles (<1 μm, annexin V positive without DNA and no histones) and another larger (1–3 μm) apoptotic body-like particles containing nuclear fragments and histones, representing apoptotic bodies. Contrary to present concepts, endothelial microparticles do not contain IL-1α and do not induce neutrophilic chemokines in vitro. In contrast, the large apoptotic bodies contain the full-length IL-1α precursor and the processed mature form. In vitro, these apoptotic bodies induce monocyte chemotactic protein-1 and IL-8 chemokine secretion in an IL-1α–dependent but IL-1β–independent fashion. Injection of these apoptotic bodies into the peritoneal cavity of mice induces elevated serum neutrophil-inducing chemokines, which was prevented by cotreatment with the IL-1 receptor antagonist. Consistently, injection of these large apoptotic bodies into the peritoneal cavity induced a neutrophilic infiltration that was prevented by IL-1 blockade. Although apoptosis is ordinarily considered noninflammatory, these data demonstrate that nonphagocytosed endothelial apoptotic bodies are inflammatory, providing a vehicle for IL-1α and, therefore, constitute a unique mechanism for sterile inflammation.