Mucosal-associated invariant T (MAIT) cells contribute to protection against certain microorganism infections and play an important role in mucosal immunity. However, the role of MAIT cells remains enigmatic in autoimmune diseases. In this study, we examined the level and function of MAIT cells in patients with rheumatic diseases. MAIT cell, cytokine, and programmed death-1 (PD-1) levels were measured by flow cytometry. Circulating MAIT cell levels were significantly reduced in systemic lupus erythematosus (SLE) and rheumatoid arthritis patients. In particular, this MAIT cell deficiency was more prominent in CD8+ and double-negative T cell subsets, and significantly correlated with disease activity, such as SLE disease activity index and 28-joint disease activity score. Interestingly, MAIT cell frequency was significantly correlated with NKT cell frequency in SLE patients. IFN-γ production in MAIT cells was impaired in SLE patients, which was due to an intrinsic defect in the Ca2+/calcineurin/NFAT1 signaling pathway. In SLE patients, MAIT cells were poorly activated by α-galactosylceramide–stimulated NKT cells, thereby showing the dysfunction between MAIT cells and NKT cells. Notably, an elevated expression of PD-1 in MAIT cells and NKT cells was associated with SLE. In rheumatoid arthritis patients, MAIT cell levels were significantly higher in synovial fluid than in peripheral blood. Our study primarily demonstrates that MAIT cells are numerically and functionally deficient in SLE. In addition, we report a novel finding that this MAIT cell deficiency is associated with NKT cell deficiency and elevated PD-1 expression. These abnormalities possibly contribute to dysregulated mucosal immunity in SLE.

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IntroductionGout is characterized by episodes of intense joint inflammation in response to intra-articular monosodium urate monohydrate (MSU) crystals. miR-155 is crucial for the proinflammatory activation of human myeloid cells and antigen-driven inflammatory arthritis. The functional role of miR-155 in acute gouty arthritis has not been defined. Therefore, the aim of this study was to examine the role of miR-155 in pathogenesis of acute gouty arthritis.MethodsSamples from 14 patients with acute gouty arthritis and 10 healthy controls (HCs) were obtained. Peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) were cultured in vitro with MSU crystals, and gene expression (human miR-155 and SHIP-1) were assessed by real-time PCR. THP-1 cells were stimulated by MSU crystals and/or miR-155 transfection and then subjected to Western blot analysis. Levels of human tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-1β in cell culture supernatants were measured by Luminex. Immunohistochemistry was performed on formalin-fixed gout tissues with anti–SHIP-1 antibody. A C57BL/6 J male mouse model of gout was used to analyze the expressions of miR-155, SHIP-1, and inflammatory cytokines.ResultsThe samples from gouty arthritis were highly enriched in miR-155, with levels of expression being higher than those found in PBMC from HC. Treatment of the cells with MSU crystals strongly induced miR-155. In addition, overexpression of miR-155 in the cells decreased levels of SHIP-1 and promoted production of MSU-induced proinflammatory cytokines, such as TNF-α and IL-1β. Consistent with in vitro observations, miR-155 expression was elevated in the mouse model of gout. The production of inflammatory cytokines was markedly increased in MSU crystal induced peritonitis mice.ConclusionsOverexpression of miR-155 in the gouty SFMC leads to suppress SHIP-1 levels and enhance proinflammatory cytokines.

The phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase plays an instrumental role in host defense and contributes to microbicial killing by releasing highly reactive oxygen species. This multicomponent enzyme is composed of membrane and cytosolic components that assemble in the plasma membrane or phagolysosome. While the guanosine S-triphosphatase (GTPase) Rac2 has been shown to be a critical regulator of NADPH oxidase activity and assembly, the role of its effector, p21-activated kinase (Pak), in oxidase function has not been well defined. Using HIV-1 Tat IntroductionPhagocytes represent the first line of cellular host defense against microorganisms. This function relies in part on the ability of these cells to generate large amounts of reactive oxygen species, including superoxide anion (O 2 ⅐Ϫ ), hydroxyl radical (OH Ϫ ), and hydrogen peroxide (H 2 O 2 ). This phenomenon, known as the respiratory burst, results from activation of a multicomponent, O 2 ⅐Ϫ -producing enzyme known as the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In resting phagocytes, the NADPH oxidase complex is dormant, separated into individual cytosolic and membrane-bound components. 1,2 Upon activation by a variety of stimuli, such as chemotactic peptides, phorbol esters, or opsonized particles, the cytosolic factors translocate to the membrane and associate with flavocytochrome b 558 , a heterodimer composed of gp91 phox and p22 phox . The 4 minimally required cytosolic factors of the NADPH oxidase include p67 phox , p47 phox , p40 phox , and the Rho guanosine triphosphatase (GTPase) Rac. 1 Cell-free assay systems, in vivo experiments in Rac2 knock-out mice, as well as the clinical phenotype caused by the presence of a Rac2 mutation in an immunocompromised patient have confirmed the crucial role of Rac2 in O 2 ⅐Ϫ generation by phagocytes. [3][4][5][6] Stimulation of Rac activity, followed by association of the active GTPase with the NADPH oxidase complex, coordinates essential steps of the electron flow and facilitates activation of downstream targets. NADPH oxidase activation is highly regulated, involving a number of phosphorylation events, conformational changes in oxidase components, and protein-protein interactions. 1 While all of the oxidase components have been reported to be targets of phosphorylation and several protein kinases have been implicated in various assay systems, the actual role of all these events in regulating the oxidase in intact neutrophils remains unclear.We have previously shown that several isoforms of p21-activated kinases (Paks) are rapidly and transiently activated in chemoattractant-stimulated neutrophils. 7,8 Furthermore, we found Pak activation was dependent on heterotrimeric G-protein coupling to the N-formyl-methionyl-leucyl-phenylalanine (fMLF) receptor and occurred in concert with Rac activation. Subsequently, Dharmawardhane et al reported that Pak localizes to membrane ruffles and lamellipodia at the leading edge of polarized cells in fMLFstimulated leukocytes. 9...

Triggers of indeterminate results from interferon-gamma release assays (IGRA) in patients with rheumatic diseases are still elusive. The aim of the present study was to describe predictors of indeterminate results from IGRA in the field of rheumatology. This cross-sectional study was retrospectively performed by using a database of patients with a request for QuantiFERON-TB Gold-In Tube test (QFT-GIT) for screening of latent tuberculosis infection. The study cohort included 631 patients with rheumatic diseases. All variables influencing indeterminate QFT-GIT results were investigated by logistic regression analysis. The overall frequency of indeterminate IGRA results was 6.8 % (43/631). Those with indeterminate results were more likely to be aged ≥70 years, female, visitors in winter, suffering from systemic lupus erythematosus (SLE), and using sulfasalazine or a tumor necrosis factor (TNF)-α inhibitor. In addition, a longer incubation time of >6 h increased the odds ratio of indeterminate IGRA results. In contrast, the automated ELISA processor, ankylosing spondylitis, and the use of a non-steroidal anti-inflammatory drug decreased the likelihood of indeterminate IGRA results. Lymphopenia, thrombocytopenia, anemia, and hypoalbuminemia were significantly associated with indeterminate IGRA results. Multivariate analysis revealed that SLE, use of sulfasalazine or a TNF-α inhibitor, and a manual ELISA system were significantly independent predictors of indeterminate IGRA results. The proportion of indeterminate results in patients with rheumatic diseases is not infrequent. Careful attention to the pre-analytical conditions should minimize the indeterminate results. Automation of the ELISA process seems to be a promising solution to decrease the rate of indeterminate response.

We previously reported that energy restriction (ER) of mice attenuated age-associated increases in serum levels of interleukin-6 (IL-6). Here, we studied peripheral blood mononuclear cells (PBMC) from male rhesus monkeys to investigate the following: 1) the production of IL-6 and other cytokines become dysregulated with aging; 2) ER influences cytokine production and mRNA expression; and, 3) oxidative stress, as induced in vitro by xanthine and xanthine oxidase (X/XOD), influences cytokine mRNA and protein levels. Two types of comparisons were made as follows: 1) between normally fed young (6-9 y) and old monkeys (22-33 y); and 2) between middle-aged monkeys (15-21 y) fed either a normal energy intake or subjected to ER (for 5.5 y at 30% less than base-line intake). IL-6 protein levels and X/XOD-induced IL-6 mRNA levels in PBMC from old monkeys were significantly greater than those in PBMC from young animals. In contrast, interleukin-1beta (IL-1beta) and interleukin-8 mRNA levels were not strongly influenced by advancing age. X/XOD, which increased levels of protein carbonyls (indicative of oxidative damage) in PBMC, induced the expression of all three cytokines. ER reduced IL-6 protein and mRNA levels induced by X/XOD and the unstimulated mRNA levels of IL-1beta. These results indicate that, in a nonhuman primate model, oxidative stress may contribute to age-associated increases in the levels of certain cytokines and that adult-onset ER partially ameliorates this alteration.

Mucosal-associated invariant T (MAIT) cells have been reported to play an important role in mucosal immunity. However, little is known about the roles of MAIT cells in chronic obstructive pulmonary disease (COPD). The aims of this study were to examine the levels of circulating MAIT cells and their subsets in COPD patients and to investigate the potential relationship between clinical parameters and MAIT cell levels. Forty-five COPD patients and 57 healthy control subjects were enrolled in the study. Circulating MAIT cells and their subset levels in the peripheral blood were measured by flow cytometry. Disease grades were classified according to the GOLD criteria for the assessment of severity of COPD. Circulating MAIT cell levels were found to be significantly reduced in COPD patients. In particular, this MAIT cell deficiency was more prominent in CD8+ and double-negative T cell subsets. Interestingly, elevated serum C-reactive protein level and reduced FEV1/FVC ratio were associated with MAIT cell deficiency in COPD patients. Furthermore, the circulating MAIT levels were found to be significantly lower in patients with moderate to severe COPD than in patients with mild COPD. Our data shows that MAIT cells are numerically deficient in the peripheral blood of patients with COPD. In addition, this MAIT cell deficiency was found to reflect inflammatory activity and disease severity. These findings provide important information for monitoring the changes in MAIT cell levels and for predicting the prognosis during the disease course.