Immune imbalance of T lymphocyte subsets is a hallmark of psoriasis, but the molecular mechanisms underlying this aspect of psoriasis pathology are poorly understood. Here, we report that microRNA-210 (miR-210), a miR that is highly expressed in both psoriasis patients and mouse models, induces helper T (Th) 17 and Th1 cell differentiation but inhibits Th2 differentiation through repressing STAT6 and LYN expression, contributing to several aspects of the immune imbalance in psoriasis. Both miR-210 ablation in mice and inhibition of miR-210 by intradermal injection of antagomir-210 blocked the immune imbalance and the development of psoriasis-like inflammation in an imiquimod-induced or IL-23–induced psoriasis-like mouse model. We further showed that TGF-β and IL-23 enhance miR-210 expression by inducing HIF-1α, which recruits P300 and promotes histone H3 acetylation in the miR-210 promoter region. Our results reveal a crucial role for miR-210 in the immune imbalance of T lymphocyte subsets in psoriasis and suggest a potential therapeutic avenue.

Absent in melanoma 2 (AIM2) has been reported to be a component of inflammasomes in innate immune cells. Surprisingly, AIM2 is expressed by B cells, and higher AIM2 expression is observed in the B cells from lupus patients. To date, the inflammasome-independent function of AIM2 in B cells remains unclear. Here, we report increased expression of AIM2 in human tonsil memory and germinal center (GC) B cells and in memory B cells and plasma cells from the circulation and skin lesions of lupus patients. Conditional knockout of AIM2 in B cells reduces the CD19⁺ B-cell frequency in lymph nodes and spleens, and dampens KLH-induced IgG1-antibody production. In a pristane-induced mouse model of lupus, AIM2 deficiency in B cells attenuates lupus symptoms and reduces the frequency of GC B cells, T follicular helper (Tfh) cells, plasmablast cells, and plasma cells. Furthermore, the loss of AIM2 in human B cells leads to the increased expression of Blimp-1 and reduces the expression of Bcl-6. However, the silencing of Blimp-1 and Bcl-6 has no significant effect on AIM2 expression, indicating that AIM2 might be the upstream regulator for Blimp-1 and Bcl-6. In addition, IL-10 is found to upregulate AIM2 expression via DNA demethylation. Together, our findings reveal that AIM2 is highly expressed in the B cells of lupus patients and promotes B-cell differentiation by modulating the Bcl-6–Blimp-1 axis, providing a novel target for SLE treatment.

The trace element iron affects immune responses and vaccination, but knowledge of its role in autoimmune diseases is limited. Expansion of pathogenic T cells, especially T follicular helper (Tfh) cells, has great significance to systemic lupus erythematosus (SLE) pathogenesis. Here, we show an important role of iron in regulation of pathogenic T cell differentiation in SLE. We found that iron overload promoted Tfh cell expansion, proinflammatory cytokine secretion, and autoantibody production in lupus-prone mice. Mice treated with a high-iron diet exhibited an increased proportion of Tfh cell and antigen-specific GC response. Iron supplementation contributed to Tfh cell differentiation. In contrast, iron chelation inhibited Tfh cell differentiation. We demonstrated that the miR-21/BDH2 axis drove iron accumulation during Tfh cell differentiation and further promoted Fe²⁺-dependent TET enzyme activity and BCL6 gene demethylation. Thus, maintaining iron homeostasis might be critical for eliminating pathogenic Th cells and might help improve the management of patients with SLE.

The pathogenesis of systemic lupus erythematosus (SLE) has not yet been completely elucidated. One of the hallmarks of SLE is the production of autoantibodies by uncontrolled over-activated B cells. Early B cell factor 1 (EBF1) contributes to the development, activation, and proliferation of B cells through activation of the AKT signaling pathway. Accumulating evidence has demonstrated that several microRNAs (miRNAs) contribute to the pathogenesis of autoimmune diseases through the regulation of B cells in SLE. We aim to investigate the expression patterns of miR-1246 in B cells and its contribution to pathogenesis of SLE. Our results showed that the expression of miR-1246 was significantly decreased in B cells from SLE patients. We verified that miR-1246 specifically targeted the EBF1 messenger RNA (mRNA) by interacting with its 3′-untranslated region (3′-UTR) and regulated the expression of EBF1. Transfection of miR-1246 inhibitors into healthy B cells upregulated the expression of EBF1, enhanced B cell function, and increased the production of B cell surface co-stimulatory molecules CD40, CD80, and CD86. We also observed that abnormal activation of the AKT signaling pathway was associated with decreased P53 expression, leading to the downregulation of the miR-1246 expression; and upregulation of the miR-1246 expression reversed the responsiveness of B cells by inhibiting EBF1 expression. Activated B cells in lupus could decrease the expression of miR-1246 through the AKT-P53 signaling pathway, which in turn enhances the expression of EBF1, thereby promoting further activation of B cells. Conversely, upregulation of miR-1246 could interrupt this amplification pathway. Our findings thus provide a theoretical framework towards the research of novel biological targets in SLE treatment.

In addition to Foxp3+ CD4+ regulatory T cells (CD4+ T reg cells), Foxp3− CD8+ regulatory T cells (CD8+ T reg cells) are critical to maintain immune tolerance. However, the molecular programs that specifically control CD8+ but not CD4+ T reg cells are largely unknown. Here, we demonstrate that simultaneous disruption of both TGF-β receptor and transcription factor Eomesodermin (Eomes) in T cells results in lethal autoimmunity due to a specific defect in CD8+ but not CD4+ T reg cells. Further, TGF-β signal maintains the regulatory identity, while Eomes controls the follicular location of CD8+ T reg cells. Both TGF-β signal and Eomes coordinate to promote the homeostasis of CD8+ T reg cells. Together, we have identified a unique molecular program designed for CD8+ T reg cells.