Decreased Plasma IL‐22 Levels and Correlations with IL‐22‐Producing T Helper Cells in Patients with New‐Onset Systemic Lupus Erythematosus

Interleukin‐22 (IL‐22) and IL‐22‐producing T helper (Th) cells are involved in the pathogenesis of autoimmune diseases. However, the roles of IL‐22 and IL‐22‐producing T helper cells in systemic lupus erythematosus (SLE) remain unclear. Plasma levels of IL‐22 were measured in 41 patients with SLE (19 new‐onset and 22 relapsing patients) and 20 healthy controls by enzyme‐linked immunosorbent assay (ELISA). Meanwhile, the percentages of CD4⁺IFN‐γ⁺ (Th1), CD4⁺IL‐17⁺ (Th17) and CD4⁺IFN‐γ^?IL‐17^? IL‐22⁺ (Th22) cells in peripheral lymphocytes were determined by flow cytometry, and plasma IL‐22 autoantibodies were detected by ELISA in 19 new‐onset SLE patients and 20 healthy controls. Plasma IL‐22 levels in new‐onset SLE patients were significantly decreased compared with relapsing SLE patients and healthy controls. After treatment with prednisone and hydroxychloroquine, the levels of plasma IL‐22 in new‐onset SLE patients were obviously increased but still lower than healthy controls. There was a positive correlation between plasma IL‐22 levels and the percentages of Th22 cells, but not Th1 and Th17 cells. Moreover, plasma IL‐22 levels as well as peripheral Th17 and Th22 cells correlated with SLE disease activity index (SLEDAI) scores and erythrocyte sedimentation rate (ESR). High frequencies of plasma IL‐22 autoantibodies were detected in new‐onset SLE patients. However, IL‐22 levels did not correlate with IL‐22 autoantibody. Decreased plasma IL‐22 levels and correlation with Th22 cells may be distinct features in new‐onset SLE. Moreover, IL‐22 and Th22 cell correlated with SLE disease activity.     

Immunoregulation therapy changes the frequency of interleukin (IL)‐22+CD4+ T cells in systemic lupus erythematosus patients

T cell and T cell‐related cytokine abnormalities are involved in the pathogenesis of systemic lupus erythematosus (SLE). Our previous study showed that the interleukin (IL)‐22⁺CD4⁺T cells and IL‐22 play an important role in the pathogenesis of SLE. In this study, we aimed to investigate the effects of glucocorticoids (GCs) and immunodepressant agents on IL‐22 and IL‐22‐producing T cell subsets in SLE patients. The frequencies of peripheral blood T helper type 22 (Th22), IL‐22⁺Th17, IL‐22⁺Th1 and Th17 cells and the concentrations of serum IL‐22, IL‐17 and interferon (IFN)‐γ in SLE patients receiving 4 weeks of treatment with cyclophosphamide (CYC), methylprednisolone and hydroxychloroquine (HCQ) were characterized by flow cytometry analysis and enzyme‐linked immunosorbent assay (ELISA). The frequencies of Th22, IL‐22⁺ Th17 and Th17 cells and the concentrations of IL‐22 and IL‐17 were reduced in response to the drugs methylprednisolone, cyclophosphamide and hydroxychloroquine for 4 weeks in the majority of SLE patients. However, the percentage of Th1 cells showed no change. No differences in the levels of IL‐22 and IL‐22⁺CD4⁺ T cells were found between non‐responders and health controls either before or after therapy. IL‐22 levels were correlated positively with Th22 cells in SLE patients after treatment. These results suggest that elevated IL‐22 is correlated with IL‐22⁺CD4⁺T cells, especially Th22 cells, and may have a co‐operative or synergetic function in the immunopathogenesis of SLE. GC, CYC and HCQ treatment may regulate the production of IL‐22, possibly by correcting the IL‐22⁺CD4⁺T cells polarizations in SLE, thus providing new insights into the mechanism of GC, CYC and HCQ in the treatment of SLE.     

Oestrogen up‐regulates interleukin‐21 production by CD4+ T lymphocytes in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease in which abnormal immune responses are mediated by tissue‐binding autoantibodies and immune complex deposition. Because most SLE patients are women of child‐bearing age, oestrogen has been suggested to play an important role in SLE pathogenesis. One proposed role is to induce B‐cell activation, culminating in increased autoantibody production. Interleukin‐21 (IL‐21) has been shown to be crucial in the differentiation of activated B cells into plasma cells. We therefore hypothesized that oestrogen up‐regulates IL‐21 production and induces subsequent B‐cell activation in SLE patients. Peripheral blood was obtained from 22 SLE patients and 16 healthy controls. Expression levels of IL‐21 and its receptor in serum, peripheral blood mononuclear cells, and CD4⁺ T cells were higher in SLE patients than in healthy controls. Exposure of CD4⁺ T cells from SLE patients to 17β‐oestradiol led to a dose‐ and time‐dependent increase in IL‐21 expression, which was abolished in the presence of mitogen‐activated protein kinase (MAPK) (MAPK kinase, p38, Jun N‐terminal kinase) inhibitors. B cells from healthy controls showed increased antibody production when they were co‐cultured with oestrogen‐treated CD4⁺ T cells from SLE patients. Treatment with IL‐21 antibody abrogated the increased antibody production of the co‐culture systems. This study revealed the association between oestrogen and IL‐21 in SLE patients. Oestrogen up‐regulates IL‐21 expression of CD4⁺ T cells via MAPK‐dependent pathways in SLE patients, which in turn induces increased antibody production by B cells.     

Activation of the aryl hydrocarbon receptor affects activation and function of human monocyte‐derived dendritic cells

Aryl hydrocarbon receptor (AhR) is well known for mediating the toxic effects of dioxin‐containing pollutants, but has also been shown to be involved in the natural regulation of the immune response. In this study, we investigated the effect of AhR activation by its endogenous ligands 6‐formylindolo[3,2‐b]carbazole (FICZ) and 2‐(1′H‐indole‐3′‐carbonyl)‐thiazole‐4‐carboxylic acid methyl ester (ITE) on the differentiation, maturation and function of monocyte‐derived DCs in Behçet's disease (BD) patients. In this study, we showed that AhR activation by FICZ and ITE down‐regulated the expression of co‐stimulatory molecules including human leucocyte antigen D‐related (HLA‐DR), CD80 and CD86, while it had no effect on the expression of CD83 and CD40 on DCs derived from BD patients and normal controls. Lipopolysaccharide (LPS)‐treated dendritic cells (DCs) from active BD patients showed a higher level of interleukin (IL)‐1β, IL‐6, IL‐23 and tumour necrosis factor (TNF)‐α production. FICZ or ITE significantly inhibited the production of IL‐1β, IL‐6, IL‐23 and TNF‐α, but induced IL‐10 production by DCs derived from active BD patients and normal controls. FICZ or ITE‐treated DCs significantly inhibited the T helper type 17 (Th17) and Th1 cell response. Activation of AhR either by FICZ or ITE inhibits DC differentiation, maturation and function. Further studies are needed to investigate whether manipulation of the AhR pathway may be used to treat BD or other autoimmune diseases.     

Antigen presenting cell‐derived IL‐6 restricts Th2‐cell differentiation

The identification of DC‐derived signals orchestrating activation of Th1 and Th17 immune responses has advanced our understanding on how these inflammatory responses develop. However, whether specific signals delivered by DCs also participate in the regulation of Th2 immune responses remains largely unknown. In this study, we show that administration of antigen‐loaded, IL‐6‐deficient DCs to naïve mice induced an exacerbated Th2 response, characterized by the differentiation of GATA‐3‐expressing T lymphocytes secreting high levels of IL‐4, IL‐5, and IL‐13. Coinjection of wild type and IL‐6‐deficient bone marrow‐derived dendritic cells (BMDCs) confirmed that IL‐6 exerted a dominant, negative influence on Th2‐cell development. This finding was confirmed in vitro, where exogenously added IL‐6 was found to limit IL‐4‐induced Th2‐cell differentiation. iNKT cells were required for optimal Th2‐cell differentiation in vivo although their activation occurred independently of IL‐6 secretion by the BMDCs. Collectively, these observations identify IL‐6 secretion as a major, unsuspected, mechanism whereby DCs control the magnitude of Th2 immunity.     

Laser microdissection‐based analysis of cytokine balance in the kidneys of patients with lupus nephritis

To determine the cytokine balance in patients with lupus nephritis (LN), we analysed kidney‐infiltrating T cells. Renal biopsy samples from 15 systemic lupus erythematosus (SLE) patients were used. In accordance with the classification of International Society of Nephrology/Renal Pathology Society, they were categorized into Class III, Class III+V (Class III‐predominant group, n = 4), Class IV, Class IV+V (Class IV‐predominant group, n = 7) and Class V (n = 4) groups. The single‐cell samples of both the glomelular and interstitial infiltrating cells were captured by laser‐microdissection. The glomerular and interstitial infiltrating T cells produced interleukin (IL)‐2, IL‐4, IL‐10, IL‐13 and IL‐17 cytokines in the Class III‐predominant, Class IV‐predominant and Class V groups. Interferon‐gamma was detected only in the glomeruli of the Class III‐predominant and Class V group samples. The expression level of IL‐17 was correlated closely with clinical parameters such as haematuria, blood urea nitrogen level, SLE Disease Activity Index scores in both glomeruli and interstitium, urine protein level in glomeruli and serum creatinine and creatinine clearance levels in interstitium. This suggests that the glomerular infiltrating T cells might act as T helper type 1 (Th1), Th2 and Th17 cells while the interstitial infiltrating T cells, act as Th2 and Th17 cells in the Class III‐predominant and Class V groups. In contrast, both the glomerular and interstitial infiltrating T cells might act as Th2 and Th17 cells in the Class IV‐predominant group. The cytokine balances may be dependent upon the classification of renal pathology, and IL‐17 might play a critical role in SLE development.     

Dysregulated CD46 shedding interferes with Th1‐contraction in systemic lupus erythematosus

IFN‐γ‐producing T helper 1 (Th1) cell responses mediate protection against infections but uncontrolled Th1 activity also contributes to a broad range of autoimmune diseases. Autocrine complement activation has recently emerged as key in the induction and contraction of human Th1 immunity: activation of the complement regulator CD46 and the C3aR expressed by CD4⁺ T cells via autocrine generated ligands C3b and C3a, respectively, are critical to IFN‐γ production. Further, CD46‐mediated signals also induce co‐expression of immunosuppressive IL‐10 in Th1 cells and transition into a (self)‐regulating and contracting phase. In consequence, C3 or CD46‐deficient patients suffer from recurrent infections while dysregulation of CD46 signaling contributes to Th1 hyperactivity in rheumatoid arthritis and multiple sclerosis. Here, we report a defect in CD46‐regulated Th1 contraction in patients with systemic lupus erythematosus (SLE). We observed that MMP‐9‐mediated increased shedding of soluble CD46 by Th1 cells was associated with this defect and that inhibition of MMP‐9 activity normalized release of soluble CD46 and restored Th1 contraction in patients’ T cells. These data may deliver the first mechanistic explanation for the increased serum CD46 levels observed in SLE patients and indicate that targeting CD46‐cleaving proteases could be a novel avenue to modulate Th1 responses.     

STS‐1 promotes IFN‐α induced autophagy by activating the JAK1‐STAT1 signaling pathway in B cells

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the overexpression of IFN‐α. IFN‐α induces autophagy via the JAK1‐STAT1 signaling pathway, contributing to the pathogenesis of SLE. Recent studies reported that B cells from patients with SLE and NZB/W F1 mice had enhanced autophagy activity; however, the mechanism still remains unknown. Here, we show that the protein tyrosine phosphatase STS‐1 (suppressor of T‐cell receptor signaling 1) was significantly overexpressed in B cells from patients with SLE and MRL/lpr mice. Notably, STS‐1 promoted IFN‐α‐induced autophagy in B cells by enhancing the JAK1‐STAT1 signaling activation. STS‐1 inhibited the phosphorylation of the E3 ubiquitin protein ligase c‐cbl, and subsequently promoted IFN‐α‐induced phosphorylation of tyrosine kinase 2, leading to JAK1‐STAT1 signaling activation. Furthermore, STAT1 and JAK1 inhibitors blocked the IFN‐α‐induced autophagy promoted by STS‐1, indicating that STS‐1 promotes IFN‐α‐induced autophagy via the JAK1‐STAT1 signaling. Our results demonstrate the importance of STS‐1 in regulating IFN‐α‐induced autophagy in B cells, and this could be used as a therapeutic approach to treat SLE.     

Interleukin‐2 treatment reverses effects of cAMP‐responsive element modulator α‐over‐expressing T cells in autoimmune‐prone mice

Systemic autoimmune diseases, such as systemic lupus erythematosus (SLE), are often characterized by a failure of self‐tolerance and result in an uncontrolled activation of B cells and effector T cells. Interleukin (IL)‐2 critically maintains homeostasis of regulatory T cells (T_reg) and effector T cells in the periphery. Previously, we identified the cAMP‐responsive element modulator α (CREMα) as a major factor responsible for decreased IL‐2 production in T cells from SLE patients. Additionally, using a transgenic mouse that specifically over‐expresses CREMα in T cells (CD2CREMαtg), we provided in‐vivo evidence that CREMα indeed suppresses IL‐2 production. To analyse the effects of CREMα in an autoimmune prone mouse model we introduced a Fas mutation in the CD2CREMαtg mice (FVB/Fas^–/–CD2CREMαtg). Overexpression of CREMα strongly accelerated the lymphadenopathy and splenomegaly in the FVB/Fas^–/– mice. This was accompanied by a massive expansion of double‐negative (DN) T cells, enhanced numbers of interferon (IFN)‐γ‐producing T cells and reduced percentages of T_regs. Treatment of FVB/Fas^–/–CD2CREMαtg mice with IL‐2 restored the percentage of T_regs and reversed increased IFN‐γ production, but did not affect the number of DNTs. Our data indicate that CREMα contributes to the failure of tolerance in SLE by favouring effector T cells and decreasing regulatory T cells, partially mediated by repression of IL‐2 in vivo .     

Distinct expression of interleukin (IL)‐36α, β and γ, their antagonist IL‐36Ra and IL‐38 in psoriasis,rheumatoid arthritis and Crohn's disease

Interleukin (IL)‐36α, IL‐36β and IL‐36γ are expressed highly in skin and are involved in the pathogenesis of psoriasis, while the antagonists IL‐36Ra or IL‐38, another potential IL‐36 inhibitor, limit uncontrolled inflammation. The expression and role of IL‐36 cytokines in rheumatoid arthritis (RA) and Crohn's disease (CD) is currently debated. Here, we observed that during imiquimod‐induced mouse skin inflammation and in human psoriasis, expression of IL‐36α, γ and IL‐36Ra, but not IL‐36β and IL‐38 mRNA, was induced and correlated with IL‐1β and T helper type 17 (Th17) cytokines (IL‐17A, IL‐22, IL‐23, CCL20). In mice with collagen‐induced arthritis and in the synovium of patients with RA, IL‐36α, β, γ, IL‐36Ra and IL‐38 were all elevated and correlated with IL‐1β, CCL3, CCL4 and macrophage colony‐stimulating factor (M‐CSF), but not with Th17 cytokines. In the colon of mice with dextran sulphate sodium‐induced colitis and in patients with CD, only IL‐36α, γ and IL‐38 were induced at relatively low levels and correlated with IL‐1β and IL‐17A. We suggest that only a minor subgroup of patients with RA (17–29%) or CD (25%) had an elevated IL‐36 agonists/antagonists ratio, versus 93% of patients with psoriasis. By immunohistochemistry, IL‐36 cytokines were produced by various cell types in skin, synovium and colonic mucosa such as keratinocytes, CD68⁺ macrophages, dendritic/Langerhans cells and CD79α⁺ plasma cells. In primary cultures of monocytes or inflammatory macrophages (M1), IL‐36β and IL‐36Ra were produced constitutively, but IL‐36α, γ and IL‐38 were produced after lipopolysaccharide stimulation. These distinct expression profiles may help to explain why only subgroups of RA and CD patients have a potentially elevated IL‐36 agonists/antagonists ratio.     

Epistatic Interaction between Genetic Variants in Susceptibility Gene ETS1 Correlates with IL‐17 Levels in SLE Patients

T‐helper cells that produce IL‐17 (Th17 cells) are a subset of CD4⁺ T‐cells with pathological roles in autoimmune diseases including systemic lupus erythematosus (SLE), and ETS1 is a negative regulator of Th17 cell differentiation. Our previous work on genome‐wide association study (GWAS) identified two variants in the ETS1 gene (rs10893872 and rs1128334) as being associated with SLE. However, like many other risk alleles for complex diseases, little is known on how these genetic variants might affect disease pathogenesis. In this study, we examined serum IL‐17 levels from 283 SLE cases and observed a significant correlation between risk variants in ETS1 and serum IL‐17 concentration in patients, which suggests a potential mechanistic link between these variants and the disease. Furthermore, we found that the two variants act synergistically in influencing IL‐17 production, with evidence of significant genetic interaction between them as well as higher correlation between the haplotype formed by the risk alleles and IL‐17 level in patient serum. In addition, the correlation between ETS1 variants and IL‐17 level seems to be more significant in SLE patients manifesting renal involvement, dsDNA autoantibody production or early‐onset.     

Photosensitivity,Apoptosis, and Cytokines in the Pathogenesis of Lupus Erythematosus: a Critical Review

The underlying pathomechanisms of lupus erythematosus (LE), a multifactorial autoimmune disease, remain elusive. Due to the clinical evidence demonstrating a clear relationship between ultraviolet (UV) light exposure and skin lesions of LE, photosensitivity has been proven to be an important factor in the pathogenesis of the disease. Standardised photoprovocation with UVA and UVB irradiation has been shown to be a reliable model for evaluating photosensitivity in patients with cutaneous LE (CLE) and analysing the underlying medical conditions of the disease. In this respect, UV irradiation can cause aberrant induction of apoptosis in keratinocytes and contribute to the appearance of excessive apoptotic cells in the skin of CLE patients. Moreover, apoptotic cells that cannot be cleared by phagocytes may undergo secondary necrosis and release proinflammatory compounds and potential autoantigens, which may contribute to the inflammatory micromilieu that leads to formation of skin lesions in the disease. In addition to UV-mediated induction of apoptosis, the molecular and cellular factors that may cause the abnormal long-lasting photoreactivity in CLE include mediators of inflammation, such as cytokines and chemokines. In particular, interferons (IFNs) are important players in the early activation of the immune system and have a specific role in the immunological interface between the innate and the adaptive immune system. The fact that treatment with recombinant type I IFNs (α and β) can induce not only systemic organ manifestations but also LE-like skin lesions provides additional evidence for a pathogenetic role of these IFNs in the disease.