Introduction: Interleukin (IL)-17 is a proinflammatory cytokine that is produced largely by a unique CD4⁺ T-helper (Th) subset called Th17 cells. The development of Th17 cells is suppressed by interferon (IFN)-γ produced by Th1 cells, suggesting cross-regulation between Th17 and Th1 cells. Thus, this study analyzed the balance of CD4⁺ Th17 and Th1 cell responses in peripheral blood from patients with systemic lupus erythematosus (SLE) and healthy subjects. Methods: Twenty-five adult patients with SLE and 26 healthy subjects matched for gender and age (± 2 years) were recruited. Peripheral blood mononuclear cells (PBMCs) from patients and healthy subjects were stimulated for 4 h ex vivo with phorbol myristate acetate (PMA) and ionomycin. The frequency of CD4⁺ T cells producing IL-17 and/or IFN-γ was measured by using flow cytometry. Expression of Th17-associated chemokine receptors CCR4 and CCR6 on CD4⁺ T cells as well as plasma levels of Th17-polarizing cytokines were assessed. Disease activity was evaluated by the SLE disease activity index score (SLEDAI). Unpaired t test and Pearson correlation were used for statistical analyses. Results: Patients with SLE had an increased frequency of CD4⁺IL-17⁺ T cells compared with healthy subjects. However, the frequency of CD4⁺IFN-γ⁺ T cells was similar between the two groups, indicating an altered balance of Th17 and Th1 cell responses in SLE. Patients with SLE also had an increased frequency of CD4⁺CCR4⁺CCR6⁺ T cells that are known to produce IL-17. The frequency of CD4⁺IL-17⁺ T cells and CD4⁺CCR4⁺CCR6⁺ T cells correlated with disease activity. In measuring plasma levels of the Th17-polarizing cytokines, levels of IL-6 were higher in patients with SLE than in healthy subjects, although levels of IL-1β, IL-21, IL-23, and transforming growth factor (TGF)-β were not different between the two groups. Conclusions: We demonstrate an enhanced Th17 cell response that correlates with disease activity in patients with SLE, suggesting a role for IL-17 in the pathogenesis of lupus. Our data indicate that the mechanisms involved in balancing Th1 and Th17 regulation, as well as in producing IL-6, are aberrant in SLE, leading to an increased Th17 response. We suggest that CCR4 and CCR6 expression on CD4⁺ T cells should be considered as markers of disease activity, and that IL-17 blocking may offer a therapeutic target in SLE.

FOXP3-positive regulatory T (Treg) cells are a unique subset of T cells with immune regulatory properties. Treg cells can be induced from non-Treg CD4⁺ T cells (induced Treg [iTreg] cells) by TCR triggering, IL-2, and TGF-β or retinoic acid. 1,25-Dihyroxyvitamin D₃ [1,25(OH)₂VD₃] affects the functions of immune cells including T cells. 1,25(OH)₂VD₃ binds the nuclear VD receptor (VDR) that binds target DNA sequences known as the VD response element (VDRE). Although 1,25(OH)₂VD₃ can promote FOXP3 expression in CD4⁺ T cells with TCR triggering and IL-2, it is unknown whether this effect of 1,25(OH)₂VD₃ is mediated through direct binding of VDR to the FOXP3 gene without involving other molecules. Also, it is unclear whether FOXP3 expression in 1,25(OH)₂VD₃-induced Treg (VD-iTreg) cells is critical for the inhibitory function of these cells. In this study, we demonstrated the presence of VDREs in the intronic conserved noncoding sequence region +1714 to +2554 of the human FOXP3 gene and the enhancement of the FOXP3 promoter activity by such VDREs in response to 1,25(OH)₂VD₃. Additionally, VD-iTreg cells suppressed the proliferation of target CD4⁺ T cells and this activity was dependent on FOXP3 expression. These findings suggest that 1,25(OH)₂VD₃ can affect human immune responses by regulating FOXP3 expression in CD4⁺ T cells through direct VDR binding to the FOXP3 gene, which is essential for inhibitory function of VD-iTreg cells.

Amino acids (AAs) are necessary nutrients which act not only as building blocks in protein synthesis but also in crucial anabolic cellular signaling pathways. It has been demonstrated that SLC7A5 is a critical transporter that mediates uptake of several essential amino acids in highly proliferative tumors and activated T cells. However, the dynamics and relevance of SLC7A5 activity in monocytes/macrophages is still poorly understood. We provide evidence that SLC7A5-mediated leucine influx contributes to pro-inflammatory cytokine production via mTOR complex 1 (mTORC1)-induced glycolytic reprograming in activated human monocytes/macrophages. Moreover, expression of SLC7A5 is significantly elevated in monocytes derived from patients with rheumatoid arthritis (RA), a chronic inflammatory disease, and was also markedly induced by LPS stimulation of both monocytes and macrophages from healthy individuals. Further, pharmacological blockade or silencing of SLC7A5 led to a significant reduction of IL-1β downstream of leucine-mediated mTORC1 activation. Inhibition of SLC7A5-mediated leucine influx was linked to downregulation of glycolytic metabolism as evidenced by the decreased extracellular acidification rate, suggesting a regulatory role for this molecule in glycolytic reprograming. Furthermore, the expression of SLC7A5 on circulating monocytes from RA patients positively correlated with clinical parameters, suggesting that SLC7A5-mediated AA influx is related to inflammatory conditions.

In humans, interleukin-1β (IL-1β) has been suggested as an essential cytokine for developing IL-17– or IL-17A–producing CD4+ T helper 17 (Th17) cells. However, little is known about the relationship of IL-1 receptor expression and Th17 cell differentiation. We report here the presence of 2 distinct CD4+ T-cell populations with and without expression of IL-1RI that correlates with the capacity to produce IL-17 in naive and memory CD4+ T cells of human peripheral blood. IL-1RI+ memory CD4+ T cells had increased gene expression of IL17, RORC, and IRF4 even before T-cell receptor triggering, indicating that the effect of IL-1β is programmed in these cells via IL-1RI. Although CD4+ T cells from umbilical cord blood did not express IL-1RI, the cytokines IL-7, IL-15, and transforming growth factor-β (TGF-β) up-regulated IL-1RI expression on naive CD4+ T cells, suggesting that IL-1RI+ naive CD4+ T cells develop in periphery. Furthermore, IL-17 production from the cytokine-treated naive CD4+ T cells was induced by IL-1β and this induction was blocked by IL-1R antagonist. These results indicate that human Th17 cell differentiation is regulated via differential expression of IL-1RI, which is controlled by IL-7 and IL-15.

CT-P13 (Remsima®, Inflectra®) is a biosimilar of the infliximab reference product (RP; Remicade®) and is approved in Europe and elsewhere, mostly for the same indications as RP. The aim of this study was to compare the 54-week efficacy, immunogenicity, pharmacokinetics (PK) and safety of CT-P13 with RP in patients with ankylosing spondylitis (AS), with a focus on patient-reported outcomes (PROs). This was a multinational, double-blind, parallel-group study in patients with active AS. Participants were randomized (1:1) to receive CT-P13 (5 mg/kg) or RP (5 mg/kg) at weeks 0, 2, 6 and then every 8 weeks up to week 54. To assess responses, standardized assessment tools were used with an intention-to-treat analysis of observed data. Anti-drug antibodies (ADAs), PK parameters, and safety outcomes were also assessed. Of 250 randomized patients (n = 125 per group), 210 (84.0 %) completed 54 weeks of treatment, with similar completion rates between groups. At week 54, Assessment of Spondylo Arthritis international Society (ASAS)20 response, ASAS40 response and ASAS partial remission were comparable between treatment groups. Changes from baseline in PROs such as mean Bath Ankylosing Spondylitis Disease Activity Index (BASDAI; CT-P13 −3.1 versus RP −2.8), Bath Ankylosing Spondylitis Functional Index (BASFI; −2.9 versus –2.7), and Short Form Health Survey (SF-36) scores (9.26 versus 10.13 for physical component summary; 7.30 versus 6.54 for mental component summary) were similar between treatment groups. At 54 weeks, 19.5 % and 23.0 % of patients receiving CT-P13 and RP, respectively, had ADAs. All observed PK parameters of CT-P13 and RP, including maximum and minimum serum concentrations, were similar through 54 weeks. The influence of ADAs on PK was similar in the two treatment groups. Most adverse events were mild or moderate in severity. There was no notable difference between treatment groups in the incidence of adverse events, serious adverse events, infections and infusion-related reactions. CT-P13 and RP have highly comparable efficacy (including PROs) and PK up to week 54. Over a 1-year period, CT-P13 was well tolerated and displayed a safety profile comparable to RP; no differences in immunogenicity were observed. ClinicalTrials.gov identifier: NCT01220518 . Registered 4 October 2010.

Objectives To identify non-major histocompatibility complex susceptible genes that might contribute to Behçet's disease (BD). Methods We performed a genome-wide association study using DNA samples from a Korean population consisting of 379 BD patients and 800 controls. A replication study was performed in a Japanese population (363 BD patients and 272 controls). To evaluate the functional implication of the target single nucleotide polymorphisms (SNP), gene expression levels in peripheral T cells, allele-specific modulation of promoter activity and biological effect of mRNA knockdown were investigated. Results We found a novel association of BD to the GIMAP locus, mapped to chromosome 7q36.1 (rs1608157, p=6.01×10⁻⁸ in a minor allele dominant model; rs11769828, allele based p=1.60×10⁻⁶). A fine mapping study identified an association with four additional SNP: rs1522596 (OR=1.45, p=7.70×10⁻⁶) in GIMAP4; rs10266069 (OR=1.32, p=2.67×10⁻⁴) and rs10256482 (OR=1.27, p=5.27×10⁻⁴) in GIMAP2; and rs2286900 (OR=1.61, p=3.53×10⁻⁵) in GIMAP1 areas. Replication study using DNA samples from the Japanese population validated the significant association between BD and the GIMAP locus. The GIMAP4 promoter construct plasmid with the minor allele of rs1608157 displayed significantly lower activity than one with the major allele. Moreover, CD4 T cells from BD patients showed a lower level of GIMAP4 mRNA, and GIMAP4 knockdown was protective against Fas-mediated apoptosis. Conclusions These results suggest that a GIMAP cluster is a novel susceptibility locus for BD, which is involved in T-cell survival, and T-cell aberration can contribute to the development of BD.