A Narrative Review of the IL-18 and IL-37 Implications in the Pathogenesis of Atopic Dermatitis and Psoriasis: Prospective Treatment Targets

Atopic dermatitis and psoriasis are prevalent inflammatory skin conditions that significantly impact the quality of life of patients, with diverse treatment options available. Despite advances in understanding their underlying mechanisms, recent research highlights the significance of interleukins IL-18 and IL-37, in Th1, Th2, and Th17 inflammatory responses, closely associated with the pathogenesis of psoriasis and atopic dermatitis. Hence, IL-18 and IL-37 could potentially become therapeutic targets. This narrative review synthesizes knowledge on these interleukins, their roles in atopic dermatitis and psoriasis, and emerging treatment strategies. Findings of a literature search up to 30 May 2024, underscore a research gap in IL-37-targeted therapies. Conversely, IL-18-focused treatments have demonstrated promise in adult-onset Still's Disease, warranting further exploration for their potential efficacy in psoriasis and atopic dermatitis.

The macrophage infectivity potentiator of Trypanosoma cruzi induces innate IFN-γ and TNF-α production by human neonatal and adult blood cells through TLR2/1 and TLR4

We previously identified the recombinant (r) macrophage (M) infectivity (I) potentiator (P) of the protozoan parasite Trypanosoma cruzi (Tc) (rTcMIP) as an immuno-stimulatory protein that induces the release of IFN-γ, CCL2 and CCL3 by human cord blood cells. These cytokines and chemokines are important to direct a type 1 adaptive immune response. rTcMIP also increased the Ab response and favored the production of the Th1-related isotype IgG2a in mouse models of neonatal vaccination, indicating that rTcMIP could be used as a vaccine adjuvant to enhance T and B cell responses. In the present study, we used cord and adult blood cells, and isolated NK cells and human monocytes to investigate the pathways and to decipher the mechanism of action of the recombinant rTcMIP. We found that rTcMIP engaged TLR1/2 and TLR4 independently of CD14 and activated the MyD88, but not the TRIF, pathway to induce IFN-γ production by IL-15-primed NK cells, and TNF-α secretion by monocytes and myeloid dendritic cells. Our results also indicated that TNF-α boosted IFN-γ expression. Though cord blood cells displayed lower responses than adult cells, our results allow to consider rTcMIP as a potential pro-type 1 adjuvant that might be associated to vaccines administered in early life or later.

Interleukin-18 and IL-18BP in inflammatory dermatological diseases

Interleukin (IL)-18, an interferon-γ inducer, belongs to the IL-1 family of pleiotropic pro-inflammatory factors, and IL-18 binding protein (IL-18BP) is a native antagonist of IL-18 in vivo, regulating its activity. Moreover, IL-18 exerts an influential function in host innate and adaptive immunity, and IL-18BP has elevated levels of interferon-γ in diverse cells, suggesting that IL-18BP is a negative feedback inhibitor of IL-18-mediated immunity. Similar to IL-1β, the IL-18 cytokine is produced as an indolent precursor that requires further processing into an active cytokine by caspase-1 and mediating downstream signaling pathways through MyD88. IL-18 has been implicated to play a role in psoriasis, atopic dermatitis, rosacea, and bullous pemphigoid in human inflammatory skin diseases. Currently, IL-18BP is less explored in treating inflammatory skin diseases, while IL-18BP is being tested in clinical trials for other diseases. Thereby, IL-18BP is a prospective therapeutic target.

Pharmacokinetic Study of rhIL-18BP and Its Effect on Radiation-Induced Cytokine Changes in Mouse Serum and Intestine

Administration of recombinant human IL-18 binding protein (rhIL-18BP), a natural antagonist of IL-18, significantly increased mouse survival after lethal doses of irradiation. To further understand the roles of IL-18BP in radiation mitigation, we studied the pharmacokinetic (PK) parameters of rhIL-18BP, and the serum and intestinal cytokine changes in CD2F1 mice treated with vehicle or rhIL-18BP after 9.0 Gy total body irradiation (TBI). For the PK study, non-compartmental pharmacokinetic analysis was performed using PKsolver. Serum and intestine specimens were collected to measure 44-cytokine levels. Principal component analysis showed a clear separation of the non-irradiated samples from the irradiated samples; and partial separation with or without rhIL-18BP treatment. Cytokine clusters that were significantly correlated in the serum or intestine, respectively were identified. On the individual cytokine levels, serum and intestinal cytokines that were significantly changed by irradiation and rhIL-18BP treatment were identified. Finally, cytokines that were significantly correlated between their serum and intestinal levels were identified. The current study established the PK parameters of rhIL-18BP in mice, identified significantly changed cytokines in mouse serum and intestine after radiation exposure and rhIL-18BP treatment. Current data provide critical insights into IL-18BP's mechanism of action as a radiation mitigator.

Crosstalk between IL-15Rα+ tumor-associated macrophages and breast cancer cells reduces CD8+ T cell recruitment

Background

Interleukin‐15 (IL‐15) is a promising immunotherapeutic agent owing to its powerful immune‐activating effects. However, the clinical benefits of these treatments are limited. Crosstalk between tumor cells and immune cells plays an important role in immune escape and immunotherapy drug resistance. Herein, this study aimed to obtain in‐depth understanding of crosstalk in the tumor microenvironment for providing potential therapeutic strategies to prevent tumor progression.

Methods

T‐cell killing assays and co‐culture models were developed to determine the role of crosstalk between macrophages and tumor cells in breast cancer resistant to IL‐15. Western blotting, histological analysis, CRISPR‐Cas9 knockout, multi‐parameter flow cytometry, and tumor cell‐macrophage co‐injection mouse models were developed to examine the mechanism by which IL‐15Rα⁺ tumor‐associated macrophages (TAMs) regulate breast cancer cell resistance to IL‐15.

Results

We found that macrophages contributed to the resistance of tumor cells to IL‐15, and tumor cells induced macrophages to express high levels of the α subunit of the IL‐15 receptor (IL‐15Rα). Further investigation showed that IL‐15Rα⁺ TAMs reduced the protein levels of chemokine CX3C chemokine ligand 1 (CX3CL1) in tumor cells to inhibit the recruitment of CD8⁺ T cells by releasing the IL‐15/IL‐15Rα complex (IL‐15Rc). Administration of an IL‐15Rc blocking peptide markedly suppressed breast tumor growth and overcame the resistance of cancer cells to anti‐ programmed cell death protein 1 (PD‐1) antibody immunotherapy. Interestingly, Granulocyte‐macrophage colony‐stimulating factor (GMCSF) induced γ chain (γc) expression to promote tumor cell‐macrophage crosstalk, which facilitated tumor resistance to IL‐15. Additionally, we observed that the non‐transcriptional regulatory function of hypoxia inducible factor‐1alpha (HIF‐1α) was essential for IL‐15Rc to regulate CX3CL1 expression in tumor cells.

Conclusions

The IL‐15Rc‐HIF‐1α‐CX3CL1 signaling pathway serves as a crosstalk between macrophages and tumor cells in the tumor microenvironment of breast cancer. Targeting this pathway may provide a potential therapeutic strategy for enhancing the efficacy of cancer immunotherapy.

Molecular Signature of Neuroinflammation Induced in Cytokine-Stimulated Human Cortical Spheroids

Crucial in the pathogenesis of neurodegenerative diseases is the process of neuroinflammation that is often linked to the pro-inflammatory cytokines Tumor necrosis factor alpha (TNFα) and Interleukin-1beta (IL-1β). Human cortical spheroids (hCSs) constitute a valuable tool to study the molecular mechanisms underlying neurological diseases in a complex three-dimensional context. We recently designed a protocol to generate hCSs comprising all major brain cell types. Here we stimulate these hCSs for three time periods with TNFα and with IL-1β. Transcriptomic analysis reveals that the main process induced in the TNFα- as well as in the IL-1β-stimulated hCSs is neuroinflammation. Central in the neuroinflammatory response are endothelial cells, microglia and astrocytes, and dysregulated genes encoding cytokines, chemokines and their receptors, and downstream NFκB- and STAT-pathway components. Furthermore, we observe sets of neuroinflammation-related genes that are specifically modulated in the TNFα-stimulated and in the IL-1β-stimulated hCSs. Together, our results help to molecularly understand human neuroinflammation and thus a key mechanism of neurodegeneration.

IL-18: The Forgotten Cytokine in Dengue Immunopathogenesis

Dengue fever is an infection by the dengue virus (DENV) transmitted by vector mosquitoes. It causes many infections in tropical and subtropical countries every year, thus posing a severe disease threat. Cytokine storms, one condition where many proinflammatory cytokines are mass-produced, might lead to cellular dysfunction in tissue/organ failures and often facilitate severe dengue disease in patients. Interleukin- (IL-) 18, similar to IL-1β, is a proinflammatory cytokine produced during inflammation following inflammasome activation. Inflammatory stimuli, including microbial infections, damage signals, and cytokines, all induce the production of IL-18. High serum IL-18 is remarkably correlated with severely ill dengue patients; however, its possible roles have been less explored. Based on the clinical and basic findings, this review discusses the potential immunopathogenic role of IL-18 when it participates in DENV infection and dengue disease progression based on existing findings and related past studies.

IL-18 binding protein (IL-18BP) as a novel radiation countermeasure after radiation exposure in mice

Recent studies suggested that radiation exposure causes local and systemic inflammatory responses and induces cell and tissue damage. We have reported that IL-18 plays an important role in radiation-induced injury. Here, we demonstrate that IL-18 binding protein (IL-18BP), a natural antagonist of IL-18, was significantly increased (1.7-63 fold) in mouse serum on day 1 after 0.5-10 Gy TBI. However, this high level of IL-18BP was not sufficient to neutralize the active IL-18 in irradiated mice, resulting in a radiation dose-dependent free IL-18 increase in these mice's serum which led to pathological alterations to the irradiated cells and tissues and finally caused animal death. Administration of recombinant human (rh) IL-18BP (1.5 mg/kg) with single (24, 48 or 72 h post-TBI) or double doses (48 h and 5 days post-TBI) subcutaneous (SC) injection increased 30-day survival of CD2F1 mice after 9 Gy TBI 12.5-25% compared with the vehicle control treated group, respectively. Furthermore, the mitigative effects of rhIL-18BP included balancing the ratio of IL-18/IL-18BP and decreasing the free IL-18 levels in irradiated mouse serum and significantly increasing blood cell counts, BM hematopoietic cellularity and stem and progenitor cell clonogenicity in mouse BM. Furthermore, IL-18BP treatment inhibited the IL-18 downstream target interferon (IFN)-γ expression in mouse BM, decreased reactive oxygen species (ROS) level in the irradiated mouse heart tissues, attenuated the stress responsive factor GDF-15 (growth differentiation factor-15) and increased the intestine protector citrulline level in total body irradiated mouse serum, implicating that IL-18BP may protect multiple organs from radiation-induced inflammation and oxidative stress. Our data suggest that IL-18 plays a key role in radiation-induced cell and tissue damage and dysfunction; and for the first time demonstrated that IL-18BP counters IL-18 activation and therefore may mitigate/treat radiation-induced multiple organ injuries and increase animal survival with a wider therapeutic window from 24 h and beyond after lethal doses of radiation exposure.

Dyskeratotic cells in persistent pruritic skin lesions as a prognostic factor in adult-onset Still disease

Adult-onset Still disease (AOSD), a systemic inflammatory disorder, is characterized by high fever, evanescent rash, arthritis, and hyperferritinaemia. AOSD is also reported to be associated with other skin lesions, including persistent pruritic papules and plaques. This study aimed to assess the significance of dyskeratotic skin lesions in Japanese AOSD patients.We retrospectively assessed the histology of persistent pruritic skin lesions and evanescent rashes and the relationship between dyskeratotic cells, serum markers, and outcomes in 20 Japanese AOSD patients, comparing AOSD histology with that of dermatomyositis (DM), drug eruptions, and graft-versus-host disease (GVHD).As the results, Persistent pruritic lesions were characterized by scattered single keratinocytes with an apoptotic appearance confined to the upper layer of the epidermis and horny layer without inflammatory infiltrate. In contrast to AOSD, the histology of DM, drug eruption, and GVHD demonstrated dyskeratotic cells in all layers of the epidermis with inflammatory infiltrate. AOSD with evanescent rash showed no dyskeratotic cells. The dyskeratotic cells in pruritic AOSD lesions stained positive for ssDNA and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling, indicating apoptosis. Serum IL-18 was significantly higher in AOSD patients with dyskeratotic cells than those without, and generally required higher doses of glucocorticoids, immunosuppressants, and biologic agents. Two of ten AOSD patients with dyskeratotic cells died from hemophagocytic lymphohistiocytosis.In conclusion, Persistent pruritic AOSD skin lesions are characterized by dyskeratotic cells with apoptotic features, involving the upper layers of the epidermis. There may be a link to elevated IL-18. This dyskeratosis may be a negative prognostic indicator.

Human Tissue-Resident Mucosal-Associated Invariant T (MAIT) Cells in Renal Fibrosis and CKD

BACKGROUND

Mucosal-associated invariant T (MAIT) cells represent a specialized lymphocyte population associated with chronic inflammatory disorders. Little is known, however, about MAIT cells in diseases of the kidney, including CKD.

METHODS

To evaluate MAIT cells in human native kidneys with tubulointerstitial fibrosis, the hallmark of CKD, we used multicolor flow cytometry to identify, enumerate, and phenotype such cells from human kidney tissue biopsy samples, and immunofluorescence microscopy to localize these cells. We cocultured MAIT cells and human primary proximal tubular epithelial cells (PTECs) under hypoxic (1% oxygen) conditions to enable examination of mechanistic tubulointerstitial interactions.

RESULTS

We identified MAIT cells (CD3+ TCR Vα7.2+ CD161hi) in healthy and diseased kidney tissues, detecting expression of tissue-resident markers (CD103/CD69) on MAIT cells in both states. Tissue samples from kidneys with tubulointerstitial fibrosis had significantly elevated numbers of MAIT cells compared with either nonfibrotic samples from diseased kidneys or tissue samples from healthy kidneys. Furthermore, CD69 expression levels, also an established marker of lymphocyte activation, were significantly increased on MAIT cells from fibrotic tissue samples. Immunofluorescent analyses of fibrotic kidney tissue identified MAIT cells accumulating adjacent to PTECs. Notably, MAIT cells activated in the presence of human PTECs under hypoxic conditions (modeling the fibrotic microenvironment) displayed significantly upregulated expression of CD69 and cytotoxic molecules perforin and granzyme B; we also observed a corresponding significant increase in PTEC necrosis in these cocultures.

CONCLUSIONS

Our findings indicate that human tissue-resident MAIT cells in the kidney may contribute to the fibrotic process of CKD via complex interactions with PTECs.

Essential Kinases and Transcriptional Regulators and Their Roles in Autoimmunity

Kinases and transcriptional regulators are fundamental components of cell signaling that are expressed on many types of immune cells which are involved in secretion of cytokines, cell proliferation, differentiation, and apoptosis. Both play important roles in biological responses in health as well as in illnesses such as the autoimmune diseases which comprise at least 80 disorders. These diseases are caused by complex genetic and environmental interactions that lead to a breakage of immunologic tolerance and a disruption of the balance between self-reactive cells and regulatory cells. Kinases or transcriptional regulatory factors often have an abnormal expression in the autoimmune cells that participate in the pathogenesis of autoimmune disease. These abnormally expressed kinases or transcriptional regulators can over-activate the function of self-reactive cells to produce inflammatory cytokines or down-regulate the activity of regulatory cells, thus causing autoimmune diseases. In this review we introduce five kinds of kinase and transcriptional regulator related to autoimmune diseases, namely, members of the Janus kinase (JAK) family (JAK3 and/or tyrosine kinase 2 (TYK2)), fork head box protein 3 (Foxp3), the retinoic acid-related orphan receptor gamma t (RORγt), and T-box expressed in T cells (T-bet) factors. We also provide a mechanistic insight into how these kinases and transcriptional regulators affect the function of the immune cells related to autoimmune diseases, as well as a description of a current drug design targeting these kinases and transcriptional regulators. Understanding their exact role helps offer new therapies for control of the inflammatory responses that could lead to clinical improvement of the autoimmune diseases.

Immune microenvironment of experimental rat C6 gliomas resembles human glioblastomas

Glioblastoma (GBM) is the most aggressive primary brain tumor, with ineffective anti-tumor responses and a poor prognosis despite aggressive treatments. GBM immune microenvironment is heterogenous  and activation of specific immune populations in GBM is not fully characterized. Reliable animal models are critical for defining mechanisms of anti-tumor immunity. First we analyzed the immune subpopulations present in rat C6 gliomas. Using flow cytometry we determined kinetics of infiltration of myeloid cells and T lymphocytes into glioma-bearing brains. We found significant increases of the amoeboid, pro-tumorigenic microglia/macrophages, T helper (Th) and T regulatory (Treg) cells in tumor-bearing brains, and rare infiltrating T cytotoxic (Tc) cells. Transcriptomic analyses of glioma-bearing hemispheres revealed overexpression of invasion and immunosuppression-related genes, reflecting the immunosuppressive microenvironment. Microglia, sorted as CD11b⁺CD45^low cells from gliomas, displayed the pro-invasive and immunosuppressive type of activation. Accumulation of Th and Treg cells combined with the reduced presence of Tc lymphocytes in rat gliomas may result in the lack of effective anti–tumor responses. Transcriptional profiles of CD11b⁺ cells and composition of immune infiltrates in C6 gliomas indicate that rat C6 gliomas employ similar immune system evasion strategies as human GBMs.

Changes in expression of genes involved in antitumor immunity in mice vaccinated with tumor vaccine composed of irradiated syngeneic tumor cells and CpG oligodeoxynucleotides

In our previous studies, it has been demonstrated that in more than 80% of mice long-lasting antitumor immunity has been established following intraperitoneal (i.p.) vaccination with tumor vaccine composed of irradiated syngeneic tumor cells and CpG ODNs class C. The aim of this study was, therefore, to investigate molecular mechanisms through which this vaccine triggers the immunity and to define genes particularly involved in this process. Changes in gene expression were followed in mononuclear cells isolated from peritoneal lavages, spleens and bone marrow samples. The expression of 84 genes significant for T-cell and B-cell activation as well as genes engaged in activation of macrophages, NK cells and DCs was determined using the RT2- Profiler PCR array. It has been observed that this tumor vaccine induces the up-regulation of genes involved in activation, proliferation and survival of memory T-cells (Cd8a, Cd8b1, Prlr, Was, Cxcl12, Il12, Sftpd, Tnfrsf13c, Il15, Il18), and prevents the activation of genes involved in generation of Treg and induction of immune tolerance (Sit1, Sla2, Cd1d1, Pdcd1lg2, Pawr, Socs5, Il27, Il4). We may conclude based on results of gene expression analysis, that tumor vaccine fine-tunes the proportion of cytotoxic to regulatory lymphocytes having an important impact on the induction and maintenance of memory cells in bone marrow.

Active immunization with human interleukin-15 induces neutralizing antibodies in non-human primates

Background

Interleukin-15 is an immunostimulatory cytokine overexpressed in several autoimmune and inflammatory diseases such as Rheumatoid Arthritis, psoriasis and ulcerative colitis; thus, inhibition of IL-15-induced signaling could be clinically beneficial in these disorders. Our approach to neutralize IL-15 consisted in active immunization with structurally modified human IL-15 (mhIL-15) with the aim to induce neutralizing antibodies against native IL-15. In the present study, we characterized the antibody response in Macaca fascicularis, non-human primates that were immunized with a vaccine candidate containing mhIL-15 in Aluminum hydroxide (Alum), Montanide and Incomplete Freund’s Adjuvant.

Results

Immunization with mhIL-15 elicited a specific antibodies response that neutralized native IL-15-dependent biologic activity in a CTLL-2 cell proliferation assay. The highest neutralizing response was obtained in macaques immunized with mhIL-15 adjuvanted in Alum. This response, which was shown to be transient, also inhibited the activity of simian IL-15 and did not affect the human IL-2-induced proliferation of CTLL-2 cells. Also, in a pool of synovial fluid cells from two Rheumatoid Arthritis patients, the immune sera slightly inhibited TNF-α secretion. Finally, it was observed that this vaccine candidate neither affect animal behavior, clinical status, blood biochemistry nor the percentage of IL-15-dependent cell populations, specifically CD56⁺ NK and CD8⁺ T cells.

Conclusion

Our results indicate that vaccination with mhIL-15 induced neutralizing antibodies to native IL-15 in non-human primates. Based on this fact, we propose that this vaccine candidate could be potentially beneficial for treatment of diseases where IL-15 overexpression is associated with their pathogenesis.

The complement receptor 3 (CD11b/CD18) agonist Leukadherin-1 suppresses human innate inflammatory signalling

Complement receptor 3 (CR3, CD11b/CD18) is a multi‐functional receptor expressed predominantly on myeloid and natural killer (NK) cells. The R77H variant of CD11b, encoded by the ITGAM rs1143679 polymorphism, is associated robustly with development of the autoimmune disease systemic lupus erythematosus (SLE) and impairs CR3 function, including its regulatory role on monocyte immune signalling. The role of CR3 in NK cell function is unknown. Leukadherin‐1 is a specific small‐molecule CR3 agonist that has shown therapeutic promise in animal models of vascular injury and inflammation. We show that Leukadherin‐1 pretreatment reduces secretion of interferon (IFN)‐γ, tumour necrosis factor (TNF) and macrophage inflammatory protein (MIP)‐1β by monokine‐stimulated NK cells. It was associated with a reduction in phosphorylated signal transducer and activator of transcription (pSTAT)‐5 following interleukin (IL)‐12 + IL‐15 stimulation (P < 0·02) and increased IL‐10 secretion following IL‐12 + IL‐18 stimulation (P < 0·001). Leukadherin‐1 pretreatment also reduces secretion of IL‐1β, IL‐6 and TNF by Toll‐like receptor (TLR)‐2 and TLR‐7/8‐stimulated monocytes (P < 0·01 for all). The R77H variant did not affect NK cell response to Leukadherin‐1 using ex‐vivo cells from homozygous donors; nor did the variant influence CR3 expression by these cell types, in contrast to a recent report. These data extend our understanding of CR3 biology by demonstrating that activation potently modifies innate immune inflammatory signalling, including a previously undocumented role in NK cell function. We discuss the potential relevance of this to the pathogenesis of SLE. Leukadherin‐1 appears to mediate its anti‐inflammatory effect irrespective of the SLE‐risk genotype of CR3, providing further evidence to support its evaluation of Leukadherin‐1 as a potential therapeutic for autoimmune disease.

Pulmonary arterial hypertension in adult onset Still's disease: a case report of a severe complication

Background

Adult onset of Still’s disease (AOSD) is a rare systemic inflammatory disease. Cardiorespiratory complications are mainly represented by pleural and pericardial disorders and are less frequent than cutaneous and articular complaints. Pulmonary arterial hypertension (PAH) occurring in AOSD is rarely described in literature.

Case presentation

We present the case of a young patient who developed severe PAH 2 years after diagnosis of AOSD. This is a rare and severe complication which is probably underestimated.

Conclusions

PAH in AOSD can be lethal, and unfortunately its occurrence is unpredictable. Echocardiographic screening of AOSD patients should be evaluated in further trials. Currently, the most suitable treatment is still unknown.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-016-0237-x) contains supplementary material, which is available to authorized users.

The role of IL-18 in type 1 diabetic nephropathy: The problem and future treatment

Diabetic vascular complication is a leading cause of diabetic nephropathy, a progressive increase in urinary albumin excretion coupled with elevated blood pressure leading to declined glomerular filtration and eventually end stage renal failure. There is growing evidence that activated inflammation is contributing factor to the pathogenesis of diabetic nephropathy. Meanwhile, IL-18, a member of the IL-1 family of inflammatory cytokines, is involved in the development and progression of diabetic nephropathy. However, the benefits derived from the current therapeutics for diabetic nephropathy strategies still provide imperfect protection against renal progression. This imperfection points to the need for newer therapeutic agents that have potential to affect primary mechanisms contributing to the pathogenesis of diabetic nephropathy. Therefore, the recognition of IL-18 as significant pathogenic mediators in diabetic nephropathy leaves open the possibility of new potential therapeutic targets.

Therapeutic potential of IL-15 in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, destructive inflammatory autoimmune disease. Cytokine-mediated immunity has been found to play an important role in the pathogenesis of autoimmune diseases including RA. Recently, much attention has been paid on the role of IL-15, which is a member of the 4 α-helix bundle cytokine family. IL-15 was detected in serum and synovial fluid from RA patients and arthritis mice models. Moreover, administration of IL-15 leads to the development of severe inflammatory arthritis, suggesting that IL-15 may be therapeutically relevant in RA. Therefore, targeting IL-15 may be significantly important and valuable. In this article, we discuss the biological features and effects of IL-15 and summarize recent advances on the pathological roles of IL-15 in RA and treatment for RA.

Biomarkers predicting a need for intensive treatment in patients with early arthritis

The heterogeneous nature of rheumatoid arthritis (RA) complicates early recognition and treatment. In recent years, a growing body of evidence has demonstrated that intervention during the window of opportunity can improve the response to treatment and slow—or even stop—irreversible structural changes. Advances in therapy, such as biologic agents, and changing approaches to the disease, such as the treat to target and tight control strategies, have led to better outcomes resulting from personalized treatment to patients with different prognostic markers. The various biomarkers identified either facilitate early diagnosis or make it possible to adjust management to disease activity or poor outcomes. However, no single biomarker can bridge the gap between disease onset and prescription of the first DMARD, and traditional biomarkers do not identify all patients requiring early aggressive treatment. Furthermore, the outcomes of early arthritis cohorts are largely biased by the treatment prescribed to patients; therefore, new challenges arise in the search for prognostic biomarkers. Herein, we discuss the value of traditional and new biomarkers and suggest the need for intensive treatment as a new surrogate marker of poor prognosis that can guide therapeutic decisions in the early stages of RA.

Molecular characterization of subcutaneous panniculitis-like T-cell lymphoma reveals upregulation of immunosuppression- and autoimmunity-associated genes

Background

Subcutaneous panniculitis-like T cell lymphomas represent a rare and difficult to diagnose entity of cutaneous T cell lymphomas. SPTL affects predominantly young adults and presents with multifocal subcutaneous nodules and frequently associated autoimmune features. The pathogenesis of SPTL is not completely understood.

Methods

The aim of this study was to unravel molecular pathways critical to the SPTL pathogenesis. Therefore, we analyzed 23 skin samples from 20 newly diagnosed SPTL patients and relevant control samples of adipose and non-malignant panniculitis tissue by using gene expression microarray, quantitative PCR, and two-colour immunohistochemistry.

Results

Interestingly, indoleamine 2,3-dioxygenase (IDO-1), an immunotolerance-inducing enzyme, was among the most highly overexpressed genes in all comparisons. The expression of Th1-specific cytokines, known to be associated with autoimmune inflammation (i.e. IFNG, CXCR3, CXCL9, CXCL10, CXCL11, and CCL5), were also significantly increased. Confirmed using immunohistochemistry, the morphologically malignant lymphocytes expressed CXCR3 and CXCL9. IDO-1 expression was found both in some morphologically malignant lymphocytes rimming the adipocytes and in surrounding CD11c⁻ CD68⁻ cells but not in CD11c⁺ dendritic cells in the microenvironment. The proportion of FoxP3+ cells in SPTL exceeded that in the benign panniculitis samples.

Conclusions

Our results indicate that the up regulation of the tolerogenic IDO-1 together with the up regulation of IFNG, CXCR3 ligands, and CCL5 are features of SPTL lesions. We anticipate that the IFNG-inducible IDO-1 expression contributes to the formation of an immunosuppressive microenvironment, favorable for the malignant T cells. This study provides a relevant molecular basis for further studies exploring novel therapeutic means for subcutaneous T cell lymphoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-014-0160-2) contains supplementary material, which is available to authorized users.

Anti-inflammatory cytokines directly inhibit innate but not adaptive CD8+ T cell functions

Virus-specific CD8(+) T cells provide classical adaptive immunity by responding to cognate peptide antigen, but they may also act in an "innate" capacity by responding directly to cytokine stimulation. Here, we examined regulation of these distinct T cell functions by anti-inflammatory cytokines (interleukin-4 [IL-4], IL-10, and transforming growth factor β [TGF-β]). Innate gamma interferon (IFN-γ) production by CD8(+) T cells following exposure to IL-12 plus IL-18, IL-12 plus tumor necrosis factor alpha (TNF-α), or IL-12 plus IL-15 was inhibited by exposure to anti-inflammatory cytokines either before or shortly after stimulation. However, inhibition was not universal, as other activation parameters, including upregulation of CD25 and CD69, remained largely unaltered. In contrast, peptide-specific T cell responses were resistant to inhibition by anti-inflammatory cytokines. This was not due to downregulation of cytokine receptor expression or an inability to signal through cytokine receptors since phosphorylation of STAT proteins remained intact. These results highlight key differences in cytokine-mediated regulation of innate and adaptive T cell functions, which may help balance effective antiviral immune responses while reducing T cell-mediated immunopathology.

IMPORTANCE

This study demonstrates key differences between the regulation of "innate" and "adaptive" CD8(+) T cell functions following activation by innate cytokines or viral peptide. Innate production of IFN-γ by CD8(+) T cells following exposure to IL-12 plus IL-18, IL-12 plus TNF-α, or IL-12 plus IL-15 was inhibited by exposure to anti-inflammatory cytokines (IL-4, IL-10, and TGF-β). However, inhibition was not universal, as other activation parameters, including upregulation of CD25 and CD69, remained largely unaltered. In contrast, peptide-specific T cell responses were resistant to inhibition by anti-inflammatory cytokines. This distinct regulation of innate and adaptive T cell functions may serve to reduce T cell-mediated immunopathology while still allowing for effective antiviral responses at a site of infection.

Adult-onset Still's disease

First described in 1971, adult-onset Still's disease (AOSD) is a rare multisystemic disorder considered as a complex (multigenic) autoinflammatory syndrome. A genetic background would confer susceptibility to the development of autoinflammatory reactions to environmental triggers. Macrophage and neutrophil activation is a hallmark of AOSD which can lead to a reactive hemophagocytic lymphohistiocytosis. As in the latter disease, the cytotoxic function of natural killer cells is decreased in patients with active AOSD. IL-18 and IL-1β, two proinflammatory cytokines processed through the inflammasome machinery, are key factors in the pathogenesis of AOSD; they cause IL-6 and Th1 cytokine secretion as well as NK cell dysregulation leading to macrophage activation. The clinico-biological picture of AOSD usually includes high spiking fever with joint symptoms, evanescent skin rash, sore throat, striking neutrophilic leukocytosis, hyperferritinemia with collapsed glycosylated ferritin (<20%), and abnormal liver function tests. According to the clinical presentation of the disease at diagnosis, two AOSD phenotypes may be distinguished: i) a highly symptomatic, systemic and feverish one, which would evolve into a systemic (mono- or polycyclic) pattern; ii) a more indolent one with arthritis in the foreground and poor systemic symptomatology, which would evolve into a chronic articular pattern. Steroid- and methotrexate-refractory AOSD cases benefit now from recent insights into autoinflammatory disorders: anakinra seems to be an efficient, well tolerated, steroid-sparing treatment in systemic patterns; tocilizumab seems efficient in AOSD with active arthritis and systemic symptoms while TNFα-blockers could be interesting in chronic polyarticular refractory AOSD.

A new phenylpyrazoleanilide, y-320, inhibits interleukin 17 production and ameliorates collagen-induced arthritis in mice and cynomolgus monkeys

Interleukin (IL)-15 and IL-17 are thought to play an important role in the pathogenesis of rheumatoid arthritis (RA) because both pro-inflammatory cytokines are found in synovial fluid of RA patients. In this study, we examined the pharmacological profiles of Y-320, a new phenylpyrazoleanilide immunomodulator. Y-320 inhibited IL-17 production by CD4 T cells stimulated with IL-15 with IC₅₀ values of 20 to 60 nM. Oral administration of Y-320 (0.3 to 3 mg/kg) significantly inhibited the development and progression of arthritis and joint destruction with reduction of IL-17 mRNA expression in arthritic joints of type II collagen-induced arthritis (CIA) in DBA/1J mice. Y-320 in combination with anti-murine tumor necrosis factor-α monoclonal antibody showed a synergistic effect on mouse CIA. Moreover, therapeutic treatment with Y-320 (0.3 and 1 mg/kg orally) ameliorated CIA in cynomolgus monkeys. Our results suggest that Y-320, an orally active inhibitor for IL-17 production, provides a useful therapy for RA.

Serum interleukin-15 levels are associated with severity of pain in patients with knee osteoarthritis

Background. Inflammation plays a crucial role in the development and progression of osteoarthritis (OA). Interleukin-15 (IL-15) is a well-known proinflammatory cytokine. Objective. We aimed at evaluating the relationship between serum IL-15 levels and the severity of pain as well as radiographic progression in patients with knee OA. Methods. Two hundred and twenty-six OA patients and 106 controls were enrolled in this study. The symptomatic/radiological severity of OA was assessed by the Western Ontario McMaster University Osteoarthritis Index- (WOMAC-)pain scores/Kellgren-Lawrence (KL) grading system. Serum IL-15 levels were measured by enzyme-linked immunosorbent assay (ELISA). Results. Serum IL-15 levels were significantly higher in OA patients compared with controls. Serum IL-15 levels were independently and positively correlated with WOMAC-pain scores but not KL grades in OA patients. Conclusions. We demonstrated that increased serum IL-15 levels were independently correlated with self-reported greater pain in knee OA patients. These results suggest that IL-15 might play a crucial role in the pathogenesis of OA related pain and therapeutic interventions by blocking IL-15 signaling pathways to delay the degenerative process of OA related pain which warrants further investigations.

Nuclear factor κB2 p52 protein has a role in antiviral immunity through IκB kinase epsilon-dependent induction of Sp1 protein and interleukin 15

In this study we describe a previously unreported function for NFκB2, an NFκB family transcription factor, in antiviral immunity. NFκB2 is induced in response to poly(I:C), a mimic of viral dsRNA. Poly(I:C), acting via TLR3, induces p52-dependent transactivation of a reporter gene in a manner that requires the kinase activity of IκB kinase ε (IKKε) and the transactivating potential of RelA/p65. We identify a novel NFκB2 binding site in the promoter of the transcription factor Sp1 that is required for Sp1 gene transcription activated by poly(I:C). We show that Sp1 is required for IL-15 induction by both poly(I:C) and respiratory syncytial virus, a response that also requires NFκB2 and IKKε. Our study identifies NFκB2 as a target for IKKε in antiviral immunity and describes, for the first time, a role for NFκB2 in the regulation of gene expression in response to viral infection.

Interleukin-15 receptor α expression in inflammatory bowel disease patients before and after normalization of inflammation with infliximab

Interleukin-15 (IL-15) is a pro-inflammatory cytokine thought to contribute to the inflammation in inflammatory bowel diseases (IBD). The specific receptor chain IL-15Rα can be expressed as a transmembranous signalling receptor, or can be cleaved by a disintegrin and metalloprotease domain 17 (ADAM17) into a neutralizing, soluble receptor (sIL-15Rα). The aim of this study is to evaluate the expression of IL-15Rα in ulcerative colitis (UC) and Crohn's disease (CD) patients before and after infliximab (IFX) therapy. Gene expression of IL-15Rα, IL-15 and ADAM17 was measured at the mRNA level by quantitative reverse transcription-PCR in mucosal biopsies harvested before and after first IFX therapy. Concentrations of sIL-15Rα were measured in sera of patients by ELISA and IL-15Rα protein was localized in the gut by immunohistochemistry and immunofluorescence. Mucosal expression of IL-15Rα is increased in UC and CD patients compared with controls and it remains elevated after IFX therapy in both responder and non-responder patients. The concentration of sIL-15Rα in serum is also increased in UC patients when compared with controls and does not differ between responders and non-responders either before or after IFX. CD patients have levels of sIL-15Rα comparable to healthy controls before and after therapy. In mucosal tissues, IL-15Rα(+) cells closely resemble activated memory B cells with a pre-plasmablastic phenotype. To conclude, IBD patients have an increased expression of IL-15Rα mRNA in the mucosa. Expression is localized in B cells, suggesting that IL-15 regulates B-cell functions during bowel inflammation. No change in release of sIL-15Rα is observed in patients treated with IFX.

Natural cytotoxicity receptors: broader expression patterns and functions in innate and adaptive immune cells

Natural cytotoxicity receptors (NCRs) have been classically defined as activating receptors delivering potent signals to Natural Killer (NK) cells in order to lyze harmful cells and to produce inflammatory cytokines. Indeed, the elicitation of NK cell effector functions after engagement of NCRs with their ligands on tumor or virus infected cells without the need for prior antigen recognition is one of the main mechanisms that allow a rapid clearance of target cells. The three known NCRs, NKp46, NKp44, and NKp30, comprise a family of germ-line encoded Ig-like trans-membrane (TM) receptors. Until recently, NCRs were thought to be NK cell specific surface molecules, thus making it possible to easily distinguish NK cells from phenotypically similar cell types. Moreover, it has also been found that the surface expression of NKp46 is conserved on NK cells across mammalian species. This discovery allowed for the use of NKp46 as a reliable marker to identify NK cells in different animal models, a comparison that was not possible before due to the lack of a common and comprehensive receptor repertoire between different species. However, several studies over the recent few years indicated that NCR expression is not exclusively confined to NK cells, but is also present on populations of T as well as of NK-like lymphocytes. These insights raised the hypothesis that the induced expression of NCRs on certain T cell subsets is governed by defined mechanisms involving the engagement of the T cell receptor (TCR) and the action of pro-inflammatory cytokines. In turn, the acquisition of NCRs by T cell subsets is also associated with a functional independence of these Ig-like TM receptors from TCR signaling. Here, we review these novel findings with respect to NCR-mediated functions of NK cells and we also discuss the functional consequences of NCR expression on non-NK cells, with a particular focus on the T cell compartment.

Transcriptomic analysis identifies candidate genes and functional networks controlling the response of porcine peripheral blood mononuclear cells to mitogenic stimulation

It is difficult to obtain phenotypic data on disease susceptibility directly from swine in an industry setting. The magnitude of the proliferative response of peripheral blood mononuclear cells (PBMC) to the T cell mitogen concanavalin A (Con A) has long been used as an indirect measure of the responsiveness of the immune system to antigenic stimulation. This trait is known to exhibit moderate heritability in swine, but little is known about the identity of the genes that control the response. In this study, we carried out a time-course microarray experiment to measure gene expression at 3 different stages (3, 20, and 68 h) poststimulation of PBMC with Con A. A total of 46, 452, and 418 differentially expressed (DifEx) genes were identified at each time point, respectively. Expression changes for a subset of these genes were subsequently confirmed by real-time PCR. Functional annotation analyses of the microarray results successfully identified sets of genes involved in processes associated with multiple aspects of cell division, such as DNA and protein synthesis, and control of mitosis. However, the discovery of genes that controlled the response of PBMC to mitogen was limited with this approach, because the drastic changes in the transcriptional program necessitated by cells undergoing division masked changes in smaller immune response gene sets. Pathway and network analyses that focused on immune cells proved to be a more effective strategy for the identification of genes that coordinate aspects of the mitogenic response that are specific to PBMC. The cytokine gene IL15 was shown to be central to the highest scoring network at 20 h and affect the expression of 16 other DifEx genes, including some genes known to regulate T cell activation, such as IL7R, JUN, TNFRSF9, and ZAP70. The IL15 gene maps to a previously identified QTL interval for immune responsiveness to Con A on SSC 8, which also contains the related IL2 gene. At 68 h, a distinct downregulation of major histocompatibility complex class II antigen presentation genes was observed. Overall, the gene expression profile of the Con A-stimulated porcine PBMC points to a Th(1) bias in immune activation. Further work is required to determine whether polymorphisms linked to genes identified in this study affect this immune response trait in pig populations and whether the trait itself correlates with decreased susceptibility to intracellular pathogens in swine.

Stronger Correlation between Interleukin 18 and Soluble Fas in Lupus Nephritis Compared with Mild Lupus

Lupus nephritis (LN) is a major cause of morbidity in patients with systemic lupus erythematosus (SLE). Several cytokines and apoptotic markers such as IL-18 and soluble Fas (sFas) have been assumed to play a role in the pathogenesis of LN. Previous studies confirmed that serum concentrations of sFas and IL-18 are increased in SLE. However, only a few studies have suggested a possible correlation between IL-18 and sFas. This study was planned to continue our previous study on the correlation between those markers to evaluate this correlation in LN. Thirty-two patients with only LN and 46 patients without any major organ involvement participated in this study. SLEDAI score (except for scores related to nephritis) was the same in these two groups. In both groups, patients with any other major organ involvement were excluded. We found a significant rise in the serum concentrations of sFas (P = 0.03) and IL-18 (P = 0.02) in patients with proteinuria compared to those without it. This study showed that the correlation between sFas and IL-18 in LN (P < 0.001, r p = 0.5) is significantly stronger than it is in mild SLE (P < 0.001, r p = 0.4) with similar nonrenal SLEDAI score (P = 0.032, z = 1.85). Between these two serum markers, sFas is the only predictor of proteinuria.

Distinct populations of innate CD8+ T cells revealed in a CXCR3 reporter mouse

CXCR3, expressed mainly on activated T and NK cells, is implicated in a host of immunological conditions and can contribute either to disease resolution or pathology. We report the generation and characterization of a novel CXCR3 internal ribosome entry site bicistronic enhanced GFP reporter (CIBER) mouse in which enhanced GFP expression correlates with surface levels of CXCR3. Using CIBER mice, we identified two distinct populations of innate CD8(+) T cells based on constitutive expression of CXCR3. We demonstrate that CXCR3(+) innate CD8(+) T cells preferentially express higher levels of Ly6C and CD122, but lower levels of CCR9 compared with CXCR3(-) innate CD8(+) T cells. Furthermore, we show that CXCR3(+) innate CD8(+) T cells express higher transcript levels of antiapoptotic but lower levels of proapoptotic factors, respond more robustly to IL-2 and IL-15, and produce significantly more IFN-γ and granzyme B. Interestingly, CXCR3(+) innate CD8(+) T cells do not respond to IL-12 or IL-18 alone, but produce significant amounts of IFN-γ on stimulation with a combination of these cytokines. Taken together, these findings demonstrate that CXCR3(+) and CXCR3(-) innate CD8(+) T cells are phenotypically and functionally distinct. These newly generated CIBER mice provide a novel tool for studying the role of CXCR3 and CXCR3-expressing cells in vivo.

Cytokine-mediated programmed proliferation of virus-specific CD8(+) memory T cells

During infection, CD8(+) T cells not only respond to antigenic signals through their T cell receptor (TCR) but also incorporate inflammatory signals from cytokines produced in the local infected microenvironment. Transient TCR-mediated stimulation will result in programmed proliferation that continues despite removal of the antigenic stimulus, but it remains unclear whether brief exposure to specific cytokines will elicit similar effects. Here, we have demonstrated that brief stimulation of memory T cells with interleukin-12 (IL-12) and interleukin-18 (IL-18) results in tightly regulated programmed proliferation, in addition to acquisition of enhanced virus-specific cytokine production and cytolytic activity. CD8(+) T cells briefly exposed to IL-12 and IL-18 in vitro showed improved antiviral activity in vivo, as demonstrated by increased proliferation and reduced viremia. These results indicate that even transitory exposure to inflammatory cytokines can provide a selective advantage to infiltrating CD8(+) T cells by triggering a developmental program that is initiated prior to direct contact with virus-infected cells.

Aberrant overexpression of IL-15 initiates large granular lymphocyte leukemia through chromosomal instability and DNA hypermethylation

How inflammation causes cancer is unclear. Interleukin-15 (IL-15) is a pro-inflammatory cytokine elevated in human large granular lymphocyte (LGL) leukemia. Mice overexpressing IL-15 develop LGL leukemia. Here, we show that prolonged in vitro exposure of wild-type (WT) LGL to IL-15 results in Myc-mediated upregulation of aurora kinases, centrosome aberrancies, and aneuploidy. Simultaneously, IL-15 represses miR-29b via induction of Myc/NF-κBp65/Hdac-1, resulting in Dnmt3b overexpression and DNA hypermethylation. All this is validated in human LGL leukemia. Adoptive transfer of WT LGL cultured with IL-15 led to malignant transformation in vivo. Drug targeting that reverses miR-29b repression cures otherwise fatal LGL leukemia. We show how excessive IL-15 initiates cancer and demonstrate effective drug targeting for potential therapy of human LGL leukemia.

Proinflammatory soluble interleukin-15 receptor alpha is increased in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune and inflammatory disease in which many cytokines have been implicated. In particular, IL-15 is a cytokine involved in the inflammatory processes and bone loss. The aim of this study was to investigate the existence in synovial fluid of soluble IL-15Rα, a private receptor subunit for IL-15 which may act as an enhancer of IL-15-induced proinflammatory cytokines. Soluble IL-15Rα was quantified by a newly developed enzyme-linked immunosorbent assay (ELISA) in samples of synovial fluid from patients with RA and osteoarthritis (OA). The levels of IL-15Rα were significantly increased in RA patients compared to OA patients. Also, we studied the presence of membrane-bound IL-15 in cells from synovial fluids, another element necessary to induce pro-inflammatory cytokines through reverse signaling. Interestingly, we found high levels of IL-6 related to high levels of IL-15Rα in RA but not in OA. Thus, our results evidenced presence of IL-15Rα in synovial fluids and suggested that its pro-inflammatory effect could be related to induction of IL-6.

Adult-Onset Still's Disease: From Pathophysiology to Targeted Therapies

Adult-onset Still's disease (AOSD) is a systemic inflammatory disorder affecting primarily young individuals. The diagnosis is primarily clinical and necessitates the exclusion of a wide range of mimicking disorders. Given the lack of solid data in regard to the underlying pathogenetic mechanisms, treatment of AOSD has been for years largely empirical. Recent advances have revealed a pivotal role of several proinflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-8 (IL-8), and interleukin-18 (IL-18) in disease pathogenesis, giving rise to the development of new targeted therapies aiming at optimal disease control.

Functions of IL-15 in anti-viral immunity: multiplicity and variety

An effective immune response to an invading viral pathogen requires the combined actions of both innate and adaptive immune cells. For example, NK cells and cytotoxic CD8 T cells are capable of the direct engagement of infected cells and the mediation of antiviral responses. Both NK and CD8 T cells depend on common gamma chain (γc) cytokine signals for their development and homeostasis. The γc cytokine IL-15 is very well characterized for its role in promoting the development and homeostasis of NK cells and CD8 T cells, but emerging literature suggests that IL-15 mediates the anti-viral responses of these cell populations during an active immune response. Both NK cells and CD8 T cells must become activated, migrate to sites of infection, survive at those sites, and expand in order to maximally exert effector functions, and IL-15 can modulate each of these processes. This review focuses on the functions of IL-15 in the regulation of multiple aspects of NK and CD8 T cell biology, investigates the mechanisms by which IL-15 may exert such diverse functions, and discusses how these different facets of IL-15 biology may be therapeutically exploited to combat viral diseases.

Glutathione deficiency in type 2 diabetes impairs cytokine responses and control of intracellular bacteria

Individuals with type 2 diabetes are at increased risk of acquiring melioidosis, a disease caused by Burkholderia pseudomallei infection. Although up to half of melioidosis patients have underlying diabetes, the mechanisms involved in this increased susceptibility are unknown. We found that B. pseudomallei-infected PBMCs from diabetic patients were impaired in IL-12p70 production, which resulted in decreased IFN-γ induction and poor bacterial killing. The defect was specific to the IL-12-IFN-γ axis. Defective IL-12 production was also observed during Mycobacterium tuberculosis infection, in which diabetes is likewise known to be a strong risk factor. In contrast, IL-12 production in diabetic cells was not affected upon Salmonella enterica infection or in response to TLR2, -3, -4, and -5 ligands. Poor IL-12 production correlated with a deficiency in intracellular reduced glutathione (GSH) concentrations in diabetic patients. Addition of GSH or N-acetylcysteine to PBMCs selectively restored IL-12 and IFN-γ production and improved bacterial killing. Furthermore, the depletion of GSH in mice led to increased susceptibility to melioidosis, reduced production of IL-12p70, and poorer disease outcome. Our data thus establish a link between GSH deficiency in diabetes and increased susceptibility to melioidosis that may open up new therapeutic avenues to protect diabetic patients against some intracellular bacterial pathogens.

Interleukin 15 levels in serum may predict a severe disease course in patients with early arthritis

Background

Interleukin-15 (IL-15) is thought to be involved in the physiopathological mechanisms of RA and it can be detected in the serum and the synovial fluid of inflamed joints in patients with RA but not in patients with osteoarthritis or other inflammatory joint diseases. Therefore, the objective of this work is to analyse whether serum IL-15 (sIL-15) levels serve as a biomarker of disease severity in patients with early arthritis (EA).

Methodology and Results

Data from 190 patients in an EA register were analysed (77.2% female; median age 53 years; 6-month median disease duration at entry). Clinical and treatment information was recorded systematically, especially the prescription of disease modifying anti-rheumatic drugs. Two multivariate longitudinal analyses were performed with different dependent variables: 1) DAS28 and 2) a variable reflecting intensive treatment. Both included sIL-15 as predictive variable and other variables associated with disease severity, including rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (ACPA). Of the 171 patients (638 visits analysed) completing the follow-up, 71% suffered rheumatoid arthritis and 29% were considered as undifferentiated arthritis. Elevated sIL-15 was detected in 29% of this population and this biomarker did not overlap extensively with RF or ACPA. High sIL-15 levels (β Coefficient [95% confidence interval]: 0.12 [0.06–0.18]; p<0.001) or ACPA (0.34 [0.01–0.67]; p = 0.044) were significantly and independently associated with a higher DAS28 during follow-up, after adjusting for confounding variables such as gender, age and treatment. In addition, those patients with elevated sIL-15 had a significantly higher risk of receiving intensive treatment (RR 1.78, 95% confidence interval 1.18–2.7; p = 0.007).

Conclusions

Patients with EA displaying high baseline sIL-15 suffered a more severe disease and received more intensive treatment. Thus, sIL-15 may be a biomarker for patients that are candidates for early and more intensive treatment.

Cutaneous manifestations associated with adult-onset Still's disease: important diagnostic values

Adult-onset Still's disease (AOSD) is a systemic inflammatory condition, characterized by a high spiking fever, leukocytosis with neutrophilia, arthralgia, and skin rash. Typical skin rash is an evanescent, salmon-pink erythema predominantly involving extremities, which is included as one of the diagnostic criteria; however, recent findings show that not only typical evanescent rash but also various skin lesions are associated with AOSD. The representative characteristic skin lesion among the non-classical skin rash is called persistent pruritic papules and plaques, which presents erythematous, slightly scaly papules with linear configuration on the trunk. Interestingly, persistent pruritic papules and plaques show unique histological features such as peculiar, distinctive distribution of dyskeratotic keratinocytes in the cornified layers as well as in the epidermis. Other non-classical skin lesions include urticaria. Current insights suggest that several inflammatory cytokines such as interleukin-1 (IL-1), IL-6, IL-18, interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) play a pathogenic role in AOSD. In particular, IL-18 is suggested to play a crucial role in activating macrophages, favoring Th1 type cytokine production. IL-18 induces IFN-γ, IL-17, and TNF-α, which may play an important pathogenic role in AOSD. It is important to recognize the common and/or uncommon skin conditions of AOSD for early correct diagnosis. In this review, various skin lesions are introduced, and the complication with histiocytic necrotizing lymphadenitis (Kikuchi disease) is further discussed.

A cytokine-centric view of the pathogenesis and treatment of autoimmune arthritis

Cytokines are immune mediators that play an important role in the pathogenesis of rheumatoid arthritis (RA), an autoimmune disease that targets the synovial joints. The cytokine environment in the peripheral lymphoid tissues and the target organ (the joint) has a strong influence on the outcome of the initial events that trigger autoimmune inflammation. In susceptible individuals, these events drive inflammation and tissue damage in the joints. However, in resistant individuals, the inflammatory events are controlled effectively with minimal or no overt signs of arthritis. Animal models of human RA have permitted comprehensive investigations into the role of cytokines in the initiation, progression, and recovery phases of autoimmune arthritis. The discovery of interleukin-17 (IL-17) and its association with inflammation and autoimmune pathology has reshaped our viewpoint regarding the pathogenesis of arthritis, which previously was based on a simplistic T helper 1 (Th1)-Th2 paradigm. This review discusses the role of the newer cytokines, particularly those associated with the IL-17/IL-23 axis in arthritis. Also presented herein is the emerging information on IL-32, IL-33, and IL-35. Ongoing studies examining the role of the newer cytokines in the disease process would improve understanding of RA as well as the development of novel cytokine inhibitors that might be more efficacious than the currently available options.

IFN-α primes T- and NK-cells for IL-15-mediated signaling and cytotoxicity

Recently it has become clear that interferon (IFN)-α, a type I interferon produced rapidly in response to infection, not only plays a key role in innate immunity, but also promotes adaptive immune responses by influencing the production or function of other cytokines. During infections IFN-α fosters the production of IL-15, which plays a pivotal role in the development, survival and function of NK cells and recruitment and activation of T cells. Since these two cytokines exert overlapping functions during infections, this investigation was undertaken to study the priming effect of IFN-α on the effect of IL-15 on human T and NK cells. We show that IFN-α induces an increased expression of IL-15Rα in human activated peripheral T cells, and in CD8(+) and CD4(+) T-cell lines. Functionally, the IFN-α-enhanced IL-15Rα expression resulted in an enhanced IL-15-mediated phosphorylation of STAT5 and STAT3 followed by a further increase in IL-15Rα expression. Moreover, IFN-α significantly increased the IL-15-induced cytotoxic activity of freshly isolated T and NK cells. Taken together, our data show that IFN-α boosts signaling and functional effects of IL-15, at least in part by fostering the increased IL-15R expression, thus add new facet to the emerging role of IFN-α as an important primer of adaptive immune responses.

Anti-inflammatory treatment of uveitis with biologicals: new treatment options that reflect pathogenetic knowledge of the disease

BACKGROUND

Endogenous uveitis is a sight-threatening disease. In addition to corticosteroids, immunosuppressive agents are commonly used to treat patients with severe course. Immunosuppressive drugs act nonspecifically, rather than providing a specific interaction with the critical pathogenetic pathways of uveitis. Better knowledge of the basic mechanisms underlying uveitis and of the molecules that are important for regulating inflammation has helped to create new and more specific treatment approaches. Biological therapy for inflammatory diseases employs substances that interfere with specific molecules or pathways induced in the body during the inflammatory process.

METHODS

This review gives an overview on molecules that play a critical role in the pathogenetic process of uveitis, as has been observed in patients or the respective animal models, and summarizes the current experience with biologicals for the treatment of uveitis refractive to conventional immunosuppressives.

Exercise training versus diet-induced weight-loss on metabolic risk factors and inflammatory markers in obese subjects: a 12-week randomized intervention study

The purpose of this study was to investigate the effect of exercise training and diet-induced weight loss alone or in combination on inflammatory markers in circulation, in adipose tissue (AT) and in skeletal muscle (SM) in obese subjects. Seventy-nine obese subjects were randomized into a 12-wk intervention: 1) exercise only (EXO), 2) diet-induced weight loss using a very low energy diet (DIO), and 3) exercise and diet-induced weight-loss combined (DEX). Blood samples (metabolic and inflammatory markers) and AT and SM biopsies (mRNA expression) were collected at baseline and after 12 wk. In the EXO group the weight loss was 3.5 kg and in the DIO and DEX groups it was 12 kg in both. Vo(2max) was increased by 14-18% in the EXO and DEX groups with no changes in the DIO group. In the DIO and DEX groups, circulating levels of MCP-1, MIP-1alpha, IL-15, and IL-18 were decreased, and adiponectin was increased (P < 0.05 for all). In the EXO group, MCP-1 was decreased with 10% (P = 0.06). By combining the weight loss in all three groups, we found a correlation between the degree of weight loss and improvement in several of the inflammatory markers (P < 0.05). In AT biopsies, subjects in the DIO and DEX groups achieved a general beneficial but nonsignificant effect on the gene expression of inflammatory markers. In the EXO group, no changes in AT adipokine mRNA were found except for an increment of adiponectin (P < 0.05). In SM, the only observed change was that the gene expression of IL-6 was increased in all three groups (P < 0.05). In conclusion, rather large weight losses (>5-7%) were found to have beneficial effects on circulating inflammatory markers in these obese subjects. Aerobic exercise for 12 wk, which increased Vo(2max), was found to have no effects on circulating inflammatory markers in these obese patients. It is suggested that more intensive exercise may be necessary to affect systemic inflammation.

Toll-like receptors (TLRs) and Nod-like receptors (NLRs) in inflammatory disorders

Toll-like receptors (TLRs) and Nod-like receptors (NLRs) are two major forms of innate immune sensors, which provide immediate responses against pathogenic invasion or tissue injury. Activation of these sensors induces the recruitment of innate immune cells such as macrophages and neutrophils, initiates tissue repair processes, and results in adaptive immune activation. Abnormalities in any of these innate sensor-mediated processes may cause excessive inflammation due to either hyper responsive innate immune signaling or sustained compensatory adaptive immune activation. Recent gene association studies appear to reveal strong associations of NLR gene mutations and development of several idiopathic inflammatory disorders. In contrast, TLR polymorphisms are less often associated with inflammatory disorders. Nevertheless, TLRs are up-regulated in the affected tissue of most inflammatory disorders, suggesting TLR signaling is involved in the pathogenesis of chronic and/or idiopathic inflammatory disorders. NLR signaling results in the formation of a molecular scaffold complex (termed an inflammasome) and orchestrates with TLRs to induce IL-1beta and IL-18, both of which are important mediators in the majority of inflammatory disorders. Therefore, understanding the roles of TLRs and NLRs in the pathogenesis of chronic and idiopathic inflammatory disorders may provide novel targets for the prevention and/or treatment of many common and uncommon diseases involving inflammation.

Cytokines and cytokine profiles in human autoimmune diseases and animal models of autoimmunity

The precise pathomechanisms of human autoimmune diseases are still poorly understood. However, a deepened understanding of these is urgently needed to improve disease prevention and early detection and guide more specific treatment approaches. In recent years, many new genes and signalling pathways involved in autoimmunity with often overlapping patterns between different disease entities have been detected. Major contributions were made by experiments using DNA microarray technology, which has been used for the analysis of gene expression patterns in chronic inflammatory and autoimmune diseases, among which were rheumatoid arthritis, systemic lupus erythematosus, psoriasis, systemic sclerosis, multiple sclerosis, and type-1 diabetes. In systemic lupus erythematosus, a so-called interferon signature has been identified. In psoriasis, researchers found a particular immune signalling cluster. Moreover the identification of a new subset of inflammatory T cells, so-called Th17 T cells, secreting interleukin (IL)-17 as one of their major cytokines and the identification of the IL-23/IL-17 axis of inflammation regulation, have significantly improved our understanding of autoimmune diseases. Since a plethora of new treatment approaches using antibodies or small molecule inhibitors specifically targeting cytokines, cellular receptors, or signalling mechanisms has emerged in recent years, more individualized treatment for affected patients may be within reach in the future.