Critical importance of patient-reported outcomes for a comprehensive assessment of psoriatic arthritis patients.

Introduction: Psoriatic arthritis (PsA) is a heterogeneous, chronic inflammatory disease that negatively impacts patients' quality of life. Patient-reported outcome measures (PROMs) are used to capture patient perspectives in disease assessment, and physicians use the Disease Activity Index for Psoriatic Arthritis (DAPSA) to evaluate disease activity in PsA. The study aimed to assess the relationship between PROMs and the DAPSA score in consecutive outpatients affected by PsA. Materials and methods: A cross-sectional study was conducted from March 2018 to October 2020 at the PsA clinic of the ARNAS Civico in Palermo (Italy), enrolling outpatients with PsA. Patients were assessed for their disease activity according to the DAPSA score, and PROMs, such as PHQ-9, HAQ, FACIT-F, and PsAID, were evaluated. Linear regression analysis evaluated the relationship between the DAPSA Score and the included PROMs. Results: 158 PsA consecutive peripheral subset psoriatic arthritis outpatients were recruited. The median years of illness was 10.6 (9.3-11.9), and the median DAPSA score was 19.02 (9-33.1). The regression analysis highlighted a strong relationship between the DAPSA score and the PsAID (adjR2 26%, p < 0.0001), the FACIT-F (adjR2 25.4%, p < 0.0001), the HAQ (adjR2 23.7%, p < 0.0001), and PHQ-9 (adjR2 15%, p < 0.0001). Conclusion: PROMs are strongly associated with the DAPSA score, but it allows in-depth evaluation of the impact of the disease on different domains of PsA patients' life.

Type 3 innate lymphoid cells producing IL-17 and IL-22 are expanded in the gut, in the peripheral blood, synovial fluid and bone marrow of patients with ankylosing spondylitis.

BACKGROUND: The aim of the study was to better characterise the immunological origin and the behaviour of interleukin (IL)-23-responsive innate lymphoid cells (ILCs) in the gut, synovial fluid (SF) and bone marrow (BM) of patients with ankylosing spondylitis (AS). METHODS: ILC1, ILC2 and ILC3 cells were determined and characterised by confocal microscopy and flow cytometry in ileal and BM biopsies, in peripheral blood (PB) and SF mononuclear cells obtained from patients with AS and controls. Mucosal vascular addressin cell adhesion molecule 1 (MADCAM-1), IL-7, IL-15 and aggregates of lymphoid tissue inducer cells (LTi) were evaluated by immunohistochemistry. The in vitro ability of epithelial cells in driving the differentiation of ILC3 and the effect of tumour necrosis factor inhibitors (TNFi) on the frequency of ILC3 and the expression of MADCAM1 were also assessed. RESULTS: ILC3 characterised as Lyn(-)RORc(-)Tbet(+) NKp44(+) cells were significantly expanded in the gut, SF and BM of patients with AS compared with controls, produced high levels of IL-17 and IL-22 and expressed α4ß7. MADcAM1 was overexpressed in BM and ileal high endothelial venules. IL-7 was significantly increased in AS gut, especially in the context of Paneth cells, and accompanied by the presence of aggregates of c-kit/IL-7R(+) cells (LTi). In in vitro experiments, epithelial cells from patients with AS actively induced differentiation of ILC3 from LTi. TNFi efficacy was accompanied by a significant decrease in the percentage of intestinal and circulating ILC3 and in the expression of MADCAM1. CONCLUSIONS: Gut-derived IL-17(+) and IL-22(+)ILC3 are expanded in the peripheral blood, SF and inflamed BM of patients with AS, suggesting the presence of an active homing axis between the gut and the inflamed sacroiliac joints.

Activated IL-22 pathway occurs in the muscle tissues of patients with polymyositis or dermatomyositis and is correlated with disease activity.

OBJECTIVE: The aim of this study was to assess the expression of IL-22, IL-22 receptor 1 (IL-22R1), IL-22 binding protein (IL-22BP) and p-STAT3 in muscle tissue from patients with PM and DM. METHODS: Levels of IL-22, IL-22R1, IL-22BP and STAT3 mRNA were quantified by RT-PCR. The expression of IL-22, IL-22R1, IL-22BP and p-STAT3 was also analysed using immunohistochemistry. RESULTS: Significant modulation of the IL-22 pathway was observed in inflammatory myopathic tissues. In particular, a significant overexpression of IL-22 at the protein but not the mRNA level was observed in PM/DM tissues and was correlated with myositis activity. IL-22R1 aberrant expression was also observed among infiltrating mononuclear cells and necrotic muscle cells. IL-22BP, which inhibits IL-22 signalling, was expressed only in some muscle fibres in PM/DM patients. CONCLUSION: Our findings indicate that the IL-22 pathway is activated in inflammatory myopathic tissues and may be involved in the induction of muscle inflammatory processes and muscle necrosis.

Safety of etanercept and methotrexate in patients with rheumatoid arthritis and hepatitis C virus infection: a multicenter randomized clinical trial.

OBJECTIVE: To evaluate the safety and efficacy of therapy with etanercept and methotrexate (MTX) in patients with active rheumatoid arthritis (RA) and mild hepatitis C virus (HCV) infection. METHODS: In this prospective open study, 29 patients with active RA were randomly assigned to receive therapy with MTX alone, etanercept alone, or a combination of MTX and etanercept, and monitored up to 54 weeks. The primary endpoint was safety; secondary aims were efficacy as defined by the 44-joint Disease Activity Score (DAS44) and health assessment questionnaire (HAQ). Serum liver enzymes and HCV viral load were serially measured. RESULTS: In the whole cohort, aspartate aminotransferase (AST) serum levels were (mean ± SD) 35 ± 3 at entry, 39 ± 5, 41 ± 7, and 38 ± 4 at 14, 30, and 54 weeks, respectively; alanine aminotransferase (ALT) serum levels were 43 ± 5 at entry, 47 ± 5, 53 ± 9, and 50 ± 6 at 14, 30, and 54 weeks, respectively. HCV viral load was 5.6 ± 0.5 at entry, 5.9 ± 0.6, 5.7 ± 0.3, and 5.6 ± 0.6 at 14, 30, and 54 weeks, respectively. AST and ALT did not significantly change in all 3 arms of treatment, nor did HCV viral load. A significant reduction of DAS44 (p < 0.01) and HAQ (p < 0.04) was detected at 54 weeks compared to baseline. No patient discontinued the therapy because of worsening of liver disease. CONCLUSION: This study showed that patients with RA and chronic HCV and mild hepatitis may be successfully treated with etanercept and MTX without increasing the risk of hepatotoxicity and HCV replication. ClinicalTrials.gov Identifier NCT01543594.

Macrophage phenotype in the subclinical gut inflammation of patients with ankylosing spondylitis.

OBJECTIVE: Long-term evolution of subclinical gut inflammation to overt Crohn's disease (CD) has been described in AS patients. The aim of this study was to evaluate macrophage polarization occurring in the inflamed gut of patients with AS. METHODS: Twenty-seven HLA-B27(+) AS patients, 20 CD patients and 17 normal controls were consecutively enrolled. Classic M1 (iNOS(+)IL-10(-)), resolution phase (iNOS(+)IL-10(+)), M2 and CD14(+) macrophages were characterized by immunohistochemistry and flow cytometry. Quantitative gene expression analysis of IFN-γ, IL-4, IL-5, IL-33 and STAT6 was performed by real time PCR. RESULTS: Classic M1 macrophages were expanded in CD and AS, where resolution phase macrophages predominate. A large increase in CD163(+) (M2) macrophages was observed in AS strictly correlated with the expression of IL-33, a Th2 cytokine involved in M2 polarization. Unlike in CD, CD14(+) macrophages were virtually absent in the gut of AS patients and controls. CONCLUSION: The absence of CD14(+) macrophages together with the expansion of resolution phase and M2 macrophages is the immunological signature of subclinical ileal inflammation in AS.

High rate of disease remission in moderate rheumatoid arthritis on etanercept therapy: data from GISEA, the Italian biologics register.

The aim of this study was to evaluate the clinical outcomes of etanercept in rheumatoid arthritis (RA) patients with moderate or severe disease activity. We analyzed data from the Italian biologics register Gruppo Italiano Studio Early Arthritides (GISEA) to investigate the rate of disease remission and functional improvement, based on the 28-Joint Disease Activity Score (DAS28) and the (Health Assessment Questionnaire (HAQ) score in RA patients with moderate or severe disease activity beginning etanercept therapy. Disease was defined as severe (H-RA) with DAS28 ≥5.1 and moderate (M-RA) with DAS28 ≥3.2 to 5.1 at baseline. Patients were considered in remission if DAS28 was ≤2.6, and HAQ ≤0.5 defined normal function. We enrolled 953 RA patients, 320 with M-RA and 633 H-RA. Age and disease duration were similar in the two cohorts, but H-RA patients had significantly more comorbidities (p < 0.01) and took significantly more disease-modifying antirheumatic drugs (p < 0.001) than M-RA patients. After 1 year, the percentage of patients achieving disease remission and normal function (DAS28 ≤2.6 plus HAQ ≤0.5) was higher in M-RA (21.4 %) than in H-RA patients (14.8 %, p = 0.007), regardless of the disease duration. Additionally, female gender (p = 0.006) and H-RA class (p = 0.002) negatively predicted disease remission at 1 year. However, the drug survival rate did not differ between the two subsets. This study confirms that etanercept was effective in the treatment of active RA, but best response, in terms of disease remission and normal function ability, was greater and easier to attain in M-RA patients. These findings may aid clinicians to choose the best strategy to treat RA.

Evidence that autophagy, but not the unfolded protein response, regulates the expression of IL-23 in the gut of patients with ankylosing spondylitis and subclinical gut inflammation.

OBJECTIVES: Interleukin (IL)-23 has been implicated in the pathogenesis of ankylosing spondylitis (AS). The aim of the study was to clarify the mechanisms underlying the increased IL-23 expression in the gut of AS patients. METHODS: Consecutive gut biopsies from 30 HLA-B27(+) AS patients, 15 Crohn's disease (CD) patients and 10 normal subjects were obtained. Evidence for HLA-B27 misfolding was studied. Unfolded protein response (UPR) and autophagy were assessed by RT-PCR and immunohistochemistry. The contribution of UPR and autophagy in the regulation of IL-23 expression was evaluated in in vitro experiments on isolated lamina propria mononuclear cells (LPMCs). RESULTS: Intracellular colocalisation of SYVN1 and FHCs but not a significant overexpression of UPR genes was observed in the gut of AS patients. Conversely, upregulation of the genes involved in the autophagy pathway was observed in the gut of AS and CD patients. Immunohistochemistry showed an increased expression of LC3II, ATG5 and ATG12 but not of SQSTM1 in the ileum of AS and CD patients. LC3II was expressed among infiltrating mononuclear cells and epithelial cells resembling Paneth cells (PC) and colocalised with ATG5 in AS and CD. Autophagy but not UPR was required to modulate the expression of IL-23 in isolated LPMCs of AS patients with chronic gut inflammation, CD patients and controls. CONCLUSIONS: Our data suggest that HLA-B27 misfolding occurs in the gut of AS patients and is accompanied by activation of autophagy rather than a UPR. Autophagy appears to be associated with intestinal modulation of IL-23 in AS.

IL-34 is overexpressed in the inflamed salivary glands of patients with Sjogren's syndrome and is associated with the local expansion of pro-inflammatory CD14(bright)CD16+ monocytes.

OBJECTIVES: To investigate the expression of IL-34 in labial salivary glands (LSGs) of patients with primary SS (p-SS) and its role in inducing a pro-inflammatory monocyte phenotype. METHODS: LSG biopsies were obtained from 20 patients with p-SS and 10 patients with non-Sjögren's sicca syndrome (n-SS). The expression of IL-34, IL-1ß, TNF-α, IL-17 and IL-23 was assessed by real-time PCR. IL-34 expression was also investigated in LSGs by immunohistochemistry. The frequencies of subpopulations of CD14(+) monocytes were evaluated by flow cytometry among isolated mononuclear cells from peripheral blood and salivary glands from both patients and controls. The role of recombinant IL-34 on isolated peripheral blood mononuclear cells was also evaluated. RESULTS: IL-34 m-RNA was overexpressed in the inflamed salivary glands of p-SS and associated with increased expression of TNF-α, IL-1ß, IL-17 and IL-23p19. The increased expression of IL-34 was confirmed by immunohistochemistry in paraffin-embedded salivary glands from p-SS patients. IL-34 expression was accompanied by the expansion of pro-inflammatory CD14(bright)CD16(+) monocytes in the salivary glands. In vitro stimulation of peripheral blood mononuclear cells with IL-34 induced the expansion of both CD14(+)CD16(-) cells and CD14(bright)CD16(+) cells in p-SS and non-SS subjects. CONCLUSION: IL-34 seems to be involved in the pathogenesis of salivary gland inflammation in p-SS.

IL-33 is overexpressed in the inflamed arteries of patients with giant cell arteritis.

OBJECTIVE: To study the expression of interleukin (IL)-33 and to evaluate its relationship with macrophage polarisation in artery biopsy specimens from patients with giant cell arteritis (GCA). METHODS: IL-33, ST2, p-STAT-6 and perivascular IL-1 receptor-associated kinase 1 (p-IRAK1) tissue distribution was evaluated by immunohistochemistry. Inducible nitric oxide synthase and CD163 were also used by immunohistochemistry to evaluate the M1 and M2 polarisation, respectively. Quantitative gene expression analysis of IL-33, T-helper (Th)2-related transcription factor STAT6, Th2 cytokines (IL-4, IL-5, IL-25) and interferon (IFN)-γ was performed in artery biopsy samples obtained from 20 patients with GCA and 15 controls. Five additional patients who had received prednisone when the temporal artery biopsy was performed were also enrolled. RESULTS: IFN-γ and IL-33 were significantly overexpressed in the inflamed arteries of GCA patients. IL-33 overexpression was not accompanied by a concomitant increase of Th2 cytokines. Neovessels scattered through the inflammatory infiltrates were the main sites of IL-33 expression. The expression of IL-33 receptor ST2 and of p-IRAK1 was also increased in GCA patients. Arteries from glucocorticoid-treated patients had a lower expression of IL-33. IL-33 was accompanied by the expression of p-STAT6 and a clear M2 macrophages polarisation. CONCLUSIONS: A role for IL-33 in the inflammation of GCA patients is supported by these findings.

Increased expression of interleukin-32 in the inflamed ileum of ankylosing spondylitis patients.

OBJECTIVE: To study the mRNA expression and protein tissue distribution of IL-32 in ileal biopsy specimens from patients with AS. METHODS: Quantitative gene expression analysis, by real-time PCR, of IL-32, IL-1ß, IL-10, TNF-α and IFN-γ was performed on ileal biopsies of 15 AS and 15 Crohn's disease (CD) patients and 10 healthy subjects (HSs). IL-32 tissue distribution was evaluated by immunohistochemistry. The effect of IL-32 on the production of IL-10 by intestinal epithelial cell lines was also evaluated. RESULTS: In the ileal specimens of patients with AS and intestinal chronic inflammation, significant up-regulation of IL-32 at both the mRNA and protein levels was found as compared with non-inflamed AS patients and controls. IL-32 over-expression in AS was accompanied by a significant increase of IL-10 but not of cytokines involved in IL-32 induction. IL-32 stimulates intestinal epithelial cell lines in vitro to produce IL-10. CONCLUSION: Our findings suggest IL-32 as an important cytokine probably involved in the innate immune response occurring in early phases of intestinal inflammation, where it seems to play a prevalent protective role.

Long-term anti-TNF therapy and the risk of serious infections in a cohort of patients with rheumatoid arthritis: comparison of adalimumab, etanercept and infliximab in the GISEA registry.

OBJECTIVE: To evaluate the risk of serious infections (SIs) in RA patients receiving anti-TNF therapy on the basis of the data included in the GISEA register. METHODS: The study involved 2769 adult patients with long-standing RA (mean age 53.2±13.4 years; mean disease duration 9.0±8.3 years) enrolled in the GISEA register, who had been treated for at least 6 months with TNF inhibitors or had discontinued therapy due to SI: 837 (30%) treated with infliximab (IFN), 802 (29%) with adalimumab (ADA), and 1130 (41%) with etanercept (ETN). RESULTS: 176 patients had experienced at least one of the 226 Sis during the 9 years of treatment with an anti-TNF agent, an overall incidence of 31.8/1000 patient-years (95% CI 25.2-38.3): 23.7/1000 patient-years (95% CI 13.1-34.2) on ADA; 12.8/1000 patient-years (95% CI 6.3-19.4) on ETN and 65.1/1000 patient-years (95% CI 48.4-81.8) on IFN. The risk was higher in the first than in the second year of treatment, but this difference was not statistically significant (p=0.08) (38.9% of the SIs were recorded in the first 12 months of treatment). The risk of SI was significantly different among the three treatment groups (p<0.0001). Multivariate models confirmed that the use of steroids (p<0.046), concomitant DMARD treatment during anti-TNF therapy (p=0.004), advanced age at the start of anti-TNF treatment (p<0.0001), and the use of IFN or ADA rather than ETN (respectively p<0.0001 and p=0.023) were strong and statistically significant predictors of infection. CONCLUSIONS: Anti-TNF therapy is associated with a small but significant risk of SI that is associated with the concomitant use of steroids, advanced age at the start of anti-TNF treatment, and the type of anti-TNF agent.

Longterm retention of tumor necrosis factor-α inhibitor therapy in a large italian cohort of patients with rheumatoid arthritis from the GISEA registry: an appraisal of predictors.

OBJECTIVE: To evaluate 4-year retention rates of tumor necrosis factor-α (TNF-α) inhibitors adalimumab, etanercept, and infliximab among patients with longstanding rheumatoid arthritis (RA), as derived from an Italian national registry. METHODS: The clinical records of 853 adult patients with RA in the GISEA (Gruppo Italiano Studio Early Arthritis) registry were prospectively analyzed to compare drug survival rates and the baseline factors that may predict adherence to therapy. RESULTS: In 2003 and 2004, 324 patients started treatment with adalimumab, 311 with etanercept, and 218 with infliximab. After 4 years, the global retention rate of anti-TNF-α therapy was 42%. Etanercept survival (51.4%) was significantly better than that of infliximab (37.6%) or adalimumab (36.4%; p < 0.0001). Accordingly, the mean duration of therapy was significantly longer for etanercept (3.1 ± 2 yrs) than for adalimumab (2.6 ± 2 yrs) or infliximab (2.7 ± 2 yrs; p < 0.05). The use of concomitant disease-modifying antirheumatic drugs, mainly methotrexate, and the presence of comorbidities significantly predicted drug continuation (p < 0.01), whereas a high Disease Activity Score did not. CONCLUSION: The 4-year global drug survival of adalimumab, etanercept, and infliximab was lower than 50%, with etanercept having the best retention rate. The main positive predictor of adherence to anti-TNF-α therapy was the concomitant use of methotrexate. Our study provides further evidence that the real-life treatment of patients with RA may be different from that of randomized clinical trials.

Expression of interleukin-32 in the inflamed arteries of patients with giant cell arteritis.

OBJECTIVE: Giant cell (temporal) arteritis (GCA) is a vasculitis that mainly affects the large and medium arteries, especially the branches of the proximal aorta. Interleukin-32 (IL-32) is a recently described Th1 proinflammatory cytokine, and is mainly induced by interferon-γ (IFNγ), IL-1ß, and tumor necrosis factor α (TNFα). This study was undertaken to investigate the expression and tissue distribution of IL-32 in artery biopsy specimens from patients with GCA. METHODS: Quantitative gene expression analysis of IL-32, IL-1ß, TNFα, IFNγ, IL-6, and IL-27 was performed in artery biopsy specimens obtained from 18 patients with GCA and 15 controls. Immunohistochemistry analysis was performed to evaluate IL-32 tissue distribution and identify IL-32-producing cells. Circulating Th1 lymphocytes were evaluated by flow cytometry. RESULTS: We demonstrated a strong and significant up-regulation of IL-32 at both the messenger RNA and protein levels in the artery biopsy samples from patients with GCA. IL-32 was abundantly expressed by vascular smooth muscle cells of inflamed arteries and neovessels within inflammatory infiltrates. IL-32 expression strongly correlated with the intensity of the systemic inflammatory response. IL-32 overexpression was accompanied by strong overexpression of Th1 cytokines, such as IFNγ and IL-27p28, in inflamed arteries from GCA patients. The Th1 lymphocyte population was also expanded among peripheral blood mononuclear cells from GCA patients and produced higher amounts of IL-32 compared to controls. CONCLUSION: Our findings indicate that overexpression of IL-32 together with a clear Th1 response immunologically characterizes the inflammatory response in GCA. In particular, IL-32 seems to be an important mediator of artery inflammation in GCA.

One year study of efficacy and safety of infliximab in the treatment of patients with ocular and neurological Behçet's disease refractory to standard immunosuppressive drugs.

The aim of the study was to assess the long-term efficacy and safety of Infliximab therapy in the treatment of patients with Behçet's disease refractory to standard immunosuppressive agents. Twenty-one patients that did not respond to corticosteroids and to at least one immunosuppressant (cyclosporin, methotrexate, azathioprine, cyclophosphamide) for the presence of ocular and/or CNS involvement were enrolled. Eighteen patients completed the study up to 54 weeks. Stable doses of prednisone (<10 mg/day) were permitted, immunosuppressants were discontinued at least 4 weeks prior baseline visit. The patients received three infusions of 5 mg/kg Infliximab (at weeks 0, 2 and 6) and then infusions of 5 mg/kg Infliximab every 8 weeks. At each visit data on clinical symptoms, response to therapy and adverse events were collected. The primary outcome of interest was to assess the clinical efficacy (total or partial recovery) of infliximab. Secondary end points were to evaluate quality of life and to monitor the safety of the drug. Eighteen patients achieved a total remission. Two patients achieved a partial remission and relapsed after 3 months from discontinuation of therapy. Infliximab was well tolerated throughout the study. A case of non-Hodgkin lymphoma was observed within 6 months. Minor side effects were headache, dizziness, tachycardia that regressed spontaneously and did not entail interruption. Anti-nuclear antibodies were not detected during the period of observation.

Expansion of intestinal CD4+CD25(high) Treg cells in patients with ankylosing spondylitis: a putative role for interleukin-10 in preventing intestinal Th17 response.

OBJECTIVE: Subclinical gut inflammation has been demonstrated in patients with ankylosing spondylitis (AS). This study was undertaken to determine the frequency of regulatory CD4+CD25(high) T cells (Treg cells) and to evaluate Treg cell-related cytokines (interleukin-2 [IL-2], transforming growth factor ß [TGFß], and IL-10) and transcription factors (FoxP3 and STAT-5) in the ileum of patients with AS. METHODS: Quantitative gene expression analysis, by reverse transcriptase-polymerase chain reaction, of Treg-related cytokines (IL-2, TGFß, and IL-10) and transcription factors (STAT-5 and FoxP3) was performed on ileal biopsy specimens from 18 patients with AS, 15 patients with active Crohn's disease (CD), and 15 healthy subjects. Tissue and circulating Treg cells were also analyzed by flow cytometry. RESULTS: A significant up-regulation of IL-2, TGFß, FoxP3, STAT-5, and IL-10 transcripts in the terminal ileum of AS patients displaying chronic ileal inflammation was observed. Flow cytometric analysis of Treg cells showed significant peripheral expansion in both patients with AS and chronic inflammation and patients with CD (mean ± SD 1.08 ± 0.4% and 1.05 ± 0.3%, respectively) as compared with healthy subjects (0.25 ± 0.12%) (P < 0.05). Interestingly, a 5-fold increase in the proportion of Treg cells was observed in the gut of patients with AS (5 ± 3%) as compared with healthy subjects (1.2 ± 0.4%) (P < 0.001), with 70-80% of these cells also producing IL-10. In vitro studies showed that blocking IL-10 was sufficient to induce Th17 polarization on lamina propria mononuclear cells isolated from AS patients. CONCLUSION: Our findings provide the first evidence that an active Treg cell response, mainly dominated by IL-10 production, occurs in the gut of AS patients and is probably responsible for the absence of a clear Th17 polarization in the ileum of AS patients.

Overexpression of interleukin-23, but not interleukin-17, as an immunologic signature of subclinical intestinal inflammation in ankylosing spondylitis.

OBJECTIVE: Subclinical gut inflammation is common in spondylarthritis, but the immunologic abnormalities underlying this process are undefined. Perturbation of the interleukin-23 (IL-23)/Th17 axis has emerged as a fundamental trigger of chronic inflammation. This study was undertaken to investigate the expression and tissue distribution of IL-23/Th17-related molecules in Crohn's disease (CD) and in subclinical gut inflammation in ankylosing spondylitis (AS). METHODS: Quantitative gene expression analysis of Th1/Th2 and IL-23/Th17 responses was performed in intestinal biopsy samples obtained from 12 patients with CD, 15 patients with AS, and 13 controls. IL-23 tissue distribution and identification of IL-23-producing cells were evaluated by immunohistochemistry. RESULTS: We demonstrated a strong and significant up-regulation of IL-23p19 transcripts in the terminal ileum in patients with AS and patients with CD. IL-23 was abundantly produced by infiltrating monocyte-like cells in inflamed mucosa from AS and CD patients. Notably, we also identified Paneth cells as a major source of IL-23 in patients with AS, patients with CD, and normal controls. Unlike CD, in AS patients, IL-23 was not associated with up-regulation of IL-17 and the IL-17-inducing cytokines IL-6 and IL-1beta. Finally, while the Th1-related cytokines interferon-gamma, IL-12p35, and IL-27p28 were overexpressed only in CD patients, IL-4, IL-5, and STAT-6 were also significantly increased in AS patients. CONCLUSION: Our findings indicate that overexpression of IL-23, but not IL-17, is a pivotal feature of subclinical gut inflammation in AS. Identification of resident Paneth cells as a pivotal source of IL-23 in physiologic and pathologic conditions strongly suggests that IL-23 is a master regulator of gut mucosal immunity, providing a pathophysiologic significance to the reported association between IL-23 receptor polymorphisms and intestinal inflammation.