Diversity of gammadelta T cells in patients with Behcet's disease is indicative of polyclonal activation

Advances in pathogenesis and treatment of ocular involvement in Behcet's disease

Behcet's disease (BD) is a chronic multi-systemic disease characterized by relapsing-remitting oral ulcers, genital ulcers, ocular inflammatory involvements, and numerous other systemic features. Ocular involvements are quite common in BD and may cause severe tissue damage and potentially blindness. Even though the pathogenesis of BD remains ambiguous, growing evidences have shown that genetic factors, environmental triggers and immunological abnormalities play significant roles in its development and progression. Novel biotherapies targeting IFN-γ, TNF-α and interleukins have been used in recent years. In this review, we mainly pay attention to the ocular involvement of BD, and discuss the current understanding of mechanisms and advances in therapeutic approaches, especially novel biologics. Finally, we discuss the management in patients with pregnancy.

γδ T cells in autoimmune uveitis pathogenesis: A promising therapeutic target

Autoimmune uveitis is a non-infectious, inflammatory intraocular disease that affects the uveal and adjacent tissues. It frequently causes varying degrees of visual loss. Evidence for the strong association between activated γδ T cells and the development of autoimmune uveitis is growing. The innate and adaptive immune response are connected in the early phases by the γδ T cells that contain the γ and δ chains. γδ T cells can identify antigens in a manner that is not constrained by the MHC. When activated by various pathways, γδ T cells can not only secrete pro-inflammatory factors early on (such as IL-17), but they can also promote Th17 cells responses, which ultimately exacerbates autoimmune uveitis. Therefore, we review the mechanisms by which γδ T cells affect autoimmune uveitis in different activation and disease states. Moreover, we also prospect for immunotherapies targeting different γδ T cell-related action pathways, providing a reference for exploring new drug for the treatment of autoimmune uveitis.

Behcet's Disease: An In-Depth Review about Pathogenesis, Gastrointestinal Manifestations, and Management

Background

Behcet's disease (BD) is a complex inflammatory vascular disorder that follows a relapsing-remitting course with diverse clinical manifestations. The prevalence of the disease varies throughout the globe and targets different age-groups. There are many variations of BD; however, intestinal BD is not only more common but has many signs and symptoms.

Summary

BD is a relapsing-remitting inflammatory vascular disorder with multiple system involvement, affecting vessels of all types and sizes that targets young adults. The etiology of BD is unknown but many factors including genetic mechanisms, vascular changes, hypercoagulability, and dysregulation of immune function are believed to be responsible. BD usually presents with signs and symptoms of ulcerative disease of the small intestine; endoscopy being consistent with the clinical manifestations. The mainstay of treatment depends upon the severity of the disease. Corticosteroids are recommended for severe forms of the disease and aminosalicylic acids are used in maintaining remission in mild to moderate forms of the disease.

Key Messages

In this review, we have tried to summarize in the present review the clinical manifestations, differential diagnoses, and management of intestinal BD. Hopefully, this review will enable health policymakers to ponder over establishing clear endpoints for treatment, surveillance investigations, and creating robust algorithms.

IL-17A and IFN-γ are Up-regulated in CD4 and γδ T Cells in Active Behcet's Disease Patients

Involvement of γδ T cells is implicated in the pathogenesis of Behçet's disease (BD) as a bridge between innate and adaptive responses. IL-17 and IL-22 have also been shown to participate in the BD pathogenesis in addition to IFN-γ. Mainly CD4⁺ T cells are investigated previously for the production of these inflammatory cytokines. In this study, the role of γδ T cells in cytokine-related mechanisms was evaluated in BD in comparison to CD4⁺ T cells. Surface expression of markers for functional states of both CD4⁺ and γδ T cells were compared in ex vivo samples collected from patients with BD and healthy controls (HC). Sixteen active BD (a-BD), 9 inactive BD (i-BD) patients and 25 HC were investigated. The expression of CD161, CCR6 as markers for IL-17 producing cells were analyzed on γδ and CD4⁺ T cells. IFN-γ, IL-17A, IL-22, as well as CD107a (LAMP1) and CD16 (FcγRIII) were evaluated in both cell subtypes after in vitro stimulation. Only IFN-γ production was increased in γδ T cells of a-BD patients. There was no difference in increase of CD107a or decrease of CD16 surface expression on γδ T cells upon stimulation between the groups. Ex vivo IL-17A and both IL-17A/IFN-γ production and expression of CD161, CCR6 by CD4⁺ T cells were increased in a-BD. Along with CD4⁺ T cells, γδ T cells have complementary roles in cytokine production in BD. Higher IFN-γ production of γδ T cells suggests the role of an environmental triggers in BD pathogenesis, whereas IL-17 related activity is mainly provided by CD4⁺ T cells.

Behçet disease: From pathogenesis to novel therapeutic options

Behçet disease (BD) is a complex, multi-systemic inflammatory condition mainly hallmarked by oral and genital ulcers which can also affect the vessels, gastrointestinal tract, central nervous system and even the axial skeleton. Without a clear classification among autoimmune or autoinflammatory conditions, BD has been recently classified as a MHC-I-opathy. BD aetiology is still obscure, but it is thought that certain microorganisms can elicit an aberrant adaptive immune response in the presence of a permissive genetic background. Altered T-cell homeostasis, mostly Th1/Th17 expansion and Treg impairment, could lead to an overactivation of the innate immunity, which underlies tissue damage and thus, signs and symptoms. Immunosuppression and/or immunomodulation are central to the BD management. A complex armamentarium ranging from classical synthetic disease-modifying antirrheumatic drugs to new-era biologic agents or small molecules is available in BD, with different therapeutic outcomes depending on disease manifestations. However, the precise disease mechanisms that underlie BD symptoms are not fully deciphered, which may limit their therapeutic potential and add a significant layer of complexity to the treatment decision-making process. The aim of the present review is to provide an exhaustive overview of the latest breakthroughs in BD pathogenesis and therapeutic options.

Succinivibrionaceae is dominant family in fecal microbiota of Behçet's Syndrome patients with uveitis

Behçet’s Syndrome (BS) is a multisystem vasculitis with various clinical manifestations. Pathogenesis is unclear, but studies have shown genetic factors, innate immunity and autoinflammation to have an important role in the disease course. Diversity in the microbial community of gut microbiota may significantly contribute to the activation of the innate immune system. The clinical features of BS present themselves in clusters and each cluster may be a consequence of different disease mechanisms. For this reason we aimed to investigate the gut microbiota of BS patients with uveitis. In addition to healthy controls, we have aimed to compare the gut microbiota of BS with that of Familial Mediterranean Fever (FMF) and Crohn’s Disease (CD) as both diseases have innate and autoinflammatory features in their pathogenesis. Seven patients with BS, 12 patients with FMF, 9 patients with CD and 16 healthy controls (HC) were included in the study. Total genomic DNAs were isolated from fecal samples of the patients. Partial 16S rRNA gene was sequenced using the PGM Ion Torrent (Thermo Fisher Scientific, Waltham, MA, USA) for microbiota analysis. Statistical analysis showed that significant differences were detected on the microbial community of four groups. Succinivibrionaceae is dominant and the signature family, whereas Bacteroides was absent in BS patients.

Behçet's Disease in Children: Diagnostic and Management Challenges

Behçet’s Disease (BD) is an inflammatory disease of unknown etiology with multisystemic involvement, being the main clinical manifestations represented by recurrent oral and genital ulcerations and uveitis. The disease has typically a chronic-relapsing course and may cause significant morbidity and mortality due to eye, vascular and neurological involvement. Although BD is more frequently diagnosed in adulthood, the disease onset can also be in pediatric age. Pediatric-onset BD is commonly featured by an incomplete clinical picture, and therefore the diagnosis represents a considerable clinical challenge for the physicians. The first classification criteria for pediatric BD, based on a scoring system, have been proposed few years ago. This work focuses on the main difficulties concerning both the diagnostic approach and the treatment of BD in pediatric age. The recommendation for the treatment of pediatric BD has been recently updated and allowed a considerable improvement of the therapeutic strategies. In particular, the use of anti-TNFα drugs as a second-line option for refractory BD, and as a first-line treatment in severe ocular and neurological involvement, has demonstrated to be effective in improving the outcome of BD patients. The knowledge about the molecular pathogenesis is progressively increasing, showing that BD shares common features with autoimmune and autoinflammatory disorders, and thus leading to the use of new biologic agents targeting the main mediators involved in the determination of BD. Anti-IL-17, anti-IL-23, anti-IL-1 and anti-IL-6 agents have shown promising results for the treatment of refractory BD in clinical trials and will represent an important alternative for the therapeutic approach to the disease.

Pediatric Behçet's disease - clinical aspects and current concepts

Behçet's Disease was first described by a Turkish dermatologist, Hulusi Behçet, in 1937 as a triple symptom complex; aphthous stomatitis, genital ulcers, and uveitis. Today, in light of current trials and experiments, we know that the disease may have a wider involvement with a multisystemic recurrent course, causing significant morbidity and mortality. However, there are still unanswered questions, particularly about Pediatric Behçet's Disease. Although several immunological and genetic associations have been demonstrated, the real etiologic mechanism of the disease is unclear. The diagnosis is difficult due to its rarity in childhood, the lack of validation of the diagnostic criteria obtained from adult studies, and the inadequacy of large case-controlled studies. Also, the management is challenging and controversial due to the various geographic distribution of clinical spectrum. New therapeutic options under development in light of pathogenetic hypothesis seem to be promising.

Behçet's disease: New insights into pathophysiology, clinical features and treatment options

Behçet's disease (BD) is a rare systemic vasculitis characterized by oral aphthous ulcers, genital ulcers, ocular lesions and other systemic manifestations. BD occurs most frequently in Eurasian populations along the ancient trading route known as the "Silk Road" which extends from eastern Asia to the Mediterranean basin. The causes of BD are unknown: it is believed to be due to an autoimmune process triggered by an infectious or environmental agent in genetically predisposed individuals. HLA-B51 allele located in the MHC locus, on chromosome 6p, has been the most strongly associated risk factor for BD in areas along the Old Silk Route. Herpes simplex virus-1 and Streptococcus have been postulated as possible environmental triggers of BD. T cell homeostasis perturbation, especially Th1 and Th17 expansion and decreased regulation by Tregs are now supposed to be the cornerstone of BD pathogenesis. The histology shows vasculitis that involves both arteries and veins, and vessels of any size. BD is a systemic vasculitis with significant neutrophil infiltration, endothelial cell swelling, and fibrinoid necrosis. The diagnosis of BD is only supported by clinical criteria and requires the exclusion of other diagnoses based on clinical presentation. There are no pathognomonic laboratorial findings of BD. This rare disease often leads to blindness and fatal systemic involvement. Main causes of death include major vessel disease and central nervous system involvement. Corticosteroids are commonly used to treat clinical manifestations of BD in combination with immunosuppressant drugs. Tumor necrosis factor (TNF)-blocking agents such as Infliximab, Etanercept, and Adalimumab have been reported to have success in patients with BD.

Update on the Medical Management of Gastrointestinal Behçet's Disease

Behçet's disease (BD) is a multisystemic disorder of unknown etiology mainly defined by recurrent oral aphthosis, genital ulcers, and chronic relapsing bilateral uveitis, all of which represent the "stigmata" of disease. However, many other organs including the vascular, neurological, musculoskeletal, and gastrointestinal systems can be affected. The gastrointestinal involvement in Behçet's disease (GIBD), along with the neurological and vascular ones, represents the most feared clinical manifestation of BD and shares many symptoms with inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis. Consequently, the differential diagnosis is often a daunting task, albeit the presence of typical endoscopic and pathologic findings may be a valuable aid to the exact diagnosis. To date, there are no standardized medical treatments for GIBD; therefore therapy should be tailored to the single patient and based on the severity of the clinical features and their complications. This work provides a digest of all current experience and evidence about pharmacological agents suggested by the medical literature as having a potential role for managing the dreadful features of GIBD.

Gamma Delta (γδ) T Cells and Their Involvement in Behçet's Disease

Behçet's disease (BD) is a multisystem inflammatory disorder characterized by orogenital ulcerations, ocular manifestations, arthritis, and vasculitis. The disease follows a relapsing-remitting course and its pathogenesis is unknown. Genetic predisposition and immune-dysregulation involving gamma delta (γδ) T cells are reported to have a role. γδ T cells are atypical T cells, which represent a small proportion of total lymphocytes. They have features of both innate and adaptive immunity and express characteristics of conventional T cells, natural killer cells, and myeloid antigen presenting cells. These unconventional T cells are found in the inflammatory BD lesions and have been suggested to be responsible for inducing and/or maintaining the proinflammatory environment characteristic of the disease. Over the last 20 years there has been much interest in the role of γδ T cells in BD. We review the literature and discuss the roles that γδ T cells may play in BD pathogenesis.

Innate immune cells in the pathogenesis of primary systemic vasculitis

Innate immune system forms the first line of defense against foreign substances. Neutrophils, eosinophils, erythrocytes, platelets, monocytes, macrophages, dendritic cells, γδ T cells, natural killer and natural killer T cells comprise the innate immune system. Genetic polymorphisms influencing the activation of innate immune cells predispose to development of vasculitis and influence its severity. Abnormally activated innate immune cells cross-talk with other cells of the innate immune system, present antigens more efficiently and activate T and B lymphocytes and cause tissue destruction via cell-mediated cytotoxicity and release of pro-inflammatory cytokines. These secreted cytokines further recruit other cells to the sites of vascular injury. They are involved in both the initiation as well as the perpetuation of vasculitis. Evidences suggest reversal of aberrant activation of immune cells in response to therapy. Understanding the role of innate immune cells in vasculitis helps understand the potential of therapeutic modulation of their activation to treat vasculitis.

Quantitative peripheral blood perturbations of γδ T cells in human disease and their clinical implications

Human γδ T cells, which play innate and adaptive, protective as well as destructive, roles in the immune response, were discovered in 1986, but the clinical significance of alterations of the levels of these cells in the peripheral blood in human diseases has not been comprehensively reviewed. Here, we review patterns of easily measurable changes of this subset of T cells in peripheral blood from relevant publications in PubMed and their correlations with specific disease categories, specific diagnoses within disease categories, and prognostic outcomes. These collective data suggest that enumeration of γδ T cells and their subsets in the peripheral blood of patients could be a useful tool to evaluate diagnosis and prognosis in the clinical setting.

Behçet's syndrome pathophysiology and potential therapeutic targets

Behçet syndrome is a systemic inflammatory disorder characterized by multiorgan involvement such as oral and genital ulcers, uveitis, skin lesions as well as by less frequent, but often more severe, central nervous system and vascular manifestations. The pathogenetic mechanisms are still incompletely known; however the interaction between a specific genetic background and environmental or infectious factors certainly contributes to the immune dysregulation that characterizes this disease. The discovery of new immunological pathways in Behçet syndrome pathogenesis may help us to set up new treatments. In this review, we will focus our attention on the possible mechanisms underlying Behçet syndrome pathogenesis and their potential role as novel therapeutic targets.

Biotherapies in Behçet's disease

Behçet's disease (BD) is a systemic large-vessel vasculitis characterized by a wide clinical spectrum including recurrent oral and genital ulcerations, uveitis, vascular, neurological, articular, renal and gastrointestinal manifestations. Therapeutic management of BD depends on the clinical presentation and organ involved. Although colchicine, nonsteroidal antiinflammatory agents and topical treatments with corticosteroids are often sufficient for mucocutaneous and joint involvements, more aggressive approach with immunosuppressive agents is warranted for severe manifestations such as posterior uveitis, retinal vasculitis, vascular, and neurological and gastrointestinal involvements. However, some patients still have refractory disease, relapse, sight threatening eye disease, or irreversible organ damage. Recent improvements in the understanding of the pathogenic mechanisms have led to the identification of potential targets and future biological therapies for BD. In contrast to current non-specific immunosuppressive agents, the emergence of biotherapies provides the possibility of interfering with specific pathogenic pathways. Novel targeted biotherapies might be used in the future for BD.

Innate and Adaptive Responses to Heat Shock Proteins in Behcet's Disease

Behcet's disease (BD) is a systemic, chronic inflammatory disorder with both innate and adaptive immune responses. Heat shock proteins (HSP) are highly conserved molecules in different species with scavenger activity and involved in correct folding of newly synthesized proteins. T and B cell responses against HSPs are observed in BD patients in both αβ and γδ T-cell populations. 60-kD HSP (HSP60) is also shown to be recognized by pattern recognition receptors such as toll-like receptors (TLR) and is suggested to be an endogenous "danger" signal to the immune system with rapid inflammatory cytokine releases and enhancement of adaptive Th1-type responses. Elucidating the exact role of HSPs in BD pathogenesis might pave the way to less toxic therapeutic approaches to BD, such as antibacterial therapies and immunomodulation.

[Pathophysiology of Behçet's disease]

Although the precise pathogenesis and etiology of Behçet's disease (BD) still remains unknown, current evidence suggests that inflammatory reaction in BD arises from disruption of homeostasis in genetically susceptible individuals, resulting in altered innate and adaptive immunity responses, pathogenic T cell activation in the peripheral blood, and in inflammatory sites. Association with HLA-B51 is known as the strongest genetic susceptibility factor for BD. Recent GWAS (genome-wide association studies) have confirmed this relationship, and reported new susceptibility genes (IL-10, IL-23R, IL-12RB2) for the disease. A triggering infectious agent could operate through molecular mimicry, and the disease could subsequently be perpetuated by an abnormal immune response to an auto-antigen in the absence of ongoing infection. Several potential bacteria have been investigated but the most commonly implicated microorganism is Streptococcus sanguis. Recent data have showed that the T cell homeostasis perturbation consisted mainly of Th1 and Th17 expansions, while regulatory T cell response was suppressed. Cytokine such as IL-17, IL-23 and IL-21 play a significant role in the pathogenesis of BD. Inflammatory cells within BD inflammatory lesions include mostly neutrophils, CD4(+) T cells, and cytotoxic cells. Lastly, endothelium dysfunction has been clearly established. This improved understanding of the pathophysiology of BD will certainly lead to the development of new therapeutic agents, potentially more effective than current therapy. In this review, we have studied the etiopathogenesis of BD in the light of recent advances.

Expression of regulatory receptors on γδ T cells and their cytokine production in Behcet's disease

INTRODUCTION

Behcet's disease (BD) is a multi-systemic disorder with muco-cutaneous, ocular, arthritic, vascular or central nervous system involvement. The role of γδ T cells is implicated in BD. The activation status of γδ T cells and their cytokine secretion against phosphoantigens are evaluated in BD.

METHODS

NKG2A, NKG2C, NKG2D, CD16 and CCR7 molecules on γδ T cells were analyzed in 70 BD, 27 tuberculosis (TB) patients and 26 healthy controls (HC). Peripheral γδ T cells were expanded with a phosphoantigen (BrHPP) and IL-2, restimulated with BrHPP and a TLR3 ligand, and cytokine production was measured.

RESULTS

γδ T cells were not increased in both BD and TB patients, but the proportions of TCRVδ2+ T cells were lower (58.9 and 50.7 vs. 71.7%, P=0.04 and P=0.005) compared to HC. Higher proportion of TCRVδ2+ T cells were CD16+ (26.2 and 33.9 vs. 16.6%, P=0.02 and P=0.001) and CCR7- (32.2 and 27.9 vs. 17.7%, P<0.0001 and P=0.014) in BD and TB patients compared to HC. NKG2C+ γδ+ T cells were relatively increased (0.5 and 0.6 vs. 0.3%, P=0.008 and 0.018), whereas NKG2D positivity was decreased in patients with BD and TB (77.7 and 75.8 vs. 87.5%, P=0.001 and 0.004). Expansion capacity of γδ T cells in BD and TB as well as production of IL-13, IFN-γ, granulocyte monocyte colony stimulating factor (GM-CSF), TNF-α, CCL4 and CCL5 in BD was lower compared to HC, when restimulated by TLR3 ligand and BrHPP.

CONCLUSION

The changes on γδ T cells of BD as well as TB patients implicate that γδ T cells have already been exposed to regulatory effects, which changed their activity. Lower cytokine response of γδ T cells implicates down modulation of these cells in BD.

NOD2 is highly expressed in Behçet disease with pulmonary manifestations

Background

Excessive Th1 cells and TLRs functions are involved in the pathogenesis of Behcet's disease (BD) in response to bacterial antigens. NOD2, an intracellular pathogen recognition sensor, modulates innate defence to muropeptides derived from various bacterial species. To further define a role for NOD2 in BD, we analysed NOD2 transcriptional responses in BAL-MNC from BD patients with pulmonary manifestations.

Methods

We analysed NOD1, NOD2, T-bet and TLRs mRNA expression with real-time polymerase chain-reaction in BAL cells obtained from 23 BD patients with pulmonary manifestations and their matched controls.

Results

We found that NOD2 mRNA expression was highly up-regulated in BAL cells from BD and sarcoidosis patients compared to healthy control group (P = 0.001). In BD patients, significant correlation was found between NOD2 and T-bet mRNA expression (r = 0.602; P = 0.0009). In BAL from BD patients, NOD2 and T-bet mRNA expression were significantly correlated with BAL-lymphocytes (r = 0.485, P = 0.010; r = 0684, P = 0.0001 respectively). NOD2 in BD was also correlated with TLR 2(r = 0.444; P = 0.021) and TLR 4 (r = 0.574; P = 0.001) mRNA expression.

Conclusion

Our results indicate that BAL-MNC from BD patients expressed NOD2 as a result of lung inflammation. TLRs and NOD2 synergize for the induction of proinflammatory cytokines. BAL inflammatory cells showed an increased Th1 situation as indicated by increased T-bet mRNA expression.

New insights into the pathogenesis of Behçet's disease

Behçet's disease (BD) is a recurrent systemic inflammatory disorder of unknown origin characterized by oral and genital mucous ulcer, uveitis, and skin lesions. Involvement of large vessels, central nervous system (CNS), gastrointestinal tract and thrombotic events are less frequent but can be life threatening. The aim of this review is to provide new insights into the pathogenesis of BD. Over the past year substantial advances have been done in the understanding of the genetic [1,2] and immunology [3] of BD. BD is at the crossroad between autoimmune and autoinflammatory syndromes. In common with autoimmune diseases BD shares class I MHC association. However, in contrast to autoimmune disorders, BD has clinical features that seem to be mostly autoinflammatory. The pathogenesis of BD is still unknown, but major determinants of the genetic and immune system abnormalities have been reported recently. Triggering infectious factors are supposed to participate in the outbreak of BD in genetically predisposed patients. Two recent large genome-wide association study (GWAS) conducted in Turkey and Japan reported association between single nucleotide polymorphism (SNP) of interleukin (IL)-10 and IL-23R/IL-12RB2 genes and BD. New insights into the perturbations of T cell homeostasis of BD recently emerged. We have recently demonstrated the promotion of Th17 responses and the suppression of regulatory T cells (Tregs) that were driven by interleukin (IL)-21 production and that correlates with BD activity. Inflammatory cells within BD inflammatory lesions included mostly neutrophils, Th1 and Th17 cells, and cytotoxic CD8+ and γδ T cells. Altogether, the recent progresses in the knowledge of BD pathogenesis pave the way for innovative therapy.

Expression of cytokines, chemokines, and chemokine receptors in oral ulcers of patients with Behcet's disease (BD) and recurrent aphthous stomatitis is Th1‐associated, although Th2‐association is also observed in patients with BD

OBJECTIVE

Although the pathogenesis of Behcet's disease (BD) is unknown, immune dysfunction appears to be involved. To improve understanding of the role of T cells and cytokines in BD, the current study analysed the localization and extent of expression of T cell subsets, cytokines, chemokines, and chemokine receptors in oral ulcers from BD patients and for comparison in oral ulcers from patients with recurrent aphthous stomatitis (RAS), as well as in healthy oral mucosa.

METHODS

Biopsies from oral ulcers of 25 BD patients and 19 RAS patients and oral mucosa from six healthy volunteers were immunoperoxidase stained.

RESULTS

Both CD4- and CD8-positive T cells were present in the oral ulcers of BD and RAS patients. The T helper (Th)1 cytokines interleukin (IL)-12, interferon (IFN)-gamma, and tumour necrosis factor (TNF)alpha and the Th1-associated chemokine receptors CCR5 and CXCR3 were increased in both patient groups as compared to normal controls, indicating the involvement of a Th1 immune response in the immunopathology of both BD and RAS. However, the Th2 cytokine IL-4 was only observed in oral ulcers of BD patients but not in RAS patients.

CONCLUSION

This is the first study that shows the presence of pro-inflammatory cytokines, as well as Th1-associated chemokine receptors, in the oral ulcers of BD patients, as well as RAS patients, at a protein level. However, the expression of the Th2 cytokine IL-4 within the oral lesions of only BD patients is suggestive of a more complex antigenic stimuli in BD patients compared with RAS patients.

Levels of IL-15 in Serum and Cerebrospinal Fluid of Patients with Behçet's Disease

Interleukin-15 (IL-15) is a novel proinflammatory cytokine, involved in the pathogenesis of inflammatory/autoimmune disease. The objective of our study was to measure serum and cerebrospinal fluid (CSF) IL-15 levels in patients with Behçet's disease (BD). CSF/serum IL-15 ratio was introduced to assess the origin of elevated IL-15 levels. We measured serum and CSF-IL-15 levels in 40 patients with BD (20 patients in active stage). Inflammatory and non-inflammatory neurological disease patients acted as controls. Active BD patients have significantly higher serum IL-15 levels (median 10.4 pg/ml; range 5.3-17.4) compared with BD in remission (6.05 pg/ml; 4-10.4) and healthy controls (4.65 pg/ml; 3.9-6.2). Similar serum IL-15 levels were found in active neuro-BD and inflammatory neurological disease (9.5 pg/ml; 5-13). Elevated levels of IL-15 were observed in CSF samples from neuro-BD patients (11 pg/ml; 8.5-15) and inflammatory neurological disease patients (10 pg/ml; 6.5-14) compared with patients with non-inflammatory neurological disease (4 pg/ml; 4-5.5; P < 0.001). Vascular cerebral BD lesions were associated with high CSF/serum IL-15 ratio. Our findings suggest that IL-15 is involved in BD inflammatory process, particularly in vasculitis foci, as an elevated CSF/serum IL-15 ratio characterizes vascular cerebral lesions.