Inflammatory monocyte-derived dendritic cells mediate autoimmunity in murine model of systemic lupus erythematosus

Type I IFN Derived from Ly6Chi Monocytes Suppresses Type 2 Inflammation in a Murine Model of Atopic Dermatitis

The roles of innate immune cells, including eosinophils, basophils, and group 2 innate lymphoid cells, in atopic dermatitis (AD) have been well-documented, whereas that of monocytes, another component of the innate immunity, remains rather poorly understood, thus necessitating the topic of this study. In addition, cytokines and cellular pathways needed for the resolution of type 2 inflammation in AD need further investigation. Using a murine AD model, we report here that (i) Ly6Chi monocytes were rapidly recruited to the AD lesion in a CCR2-dependent manner, blockade of which exacerbated AD; (ii) type I IFN production is profoundly involved in this suppression because the blockade of it by genetic depletion or antibody neutralization exacerbated AD; and (iii) Ly6Chi monocytes operate through the production of type I IFN because Ly6Chi monocytes from Irf7-null mice, which lack type I IFN production, failed to rescue Ccr2-/- mice from severe AD upon adoptive transfer. In addition, in vitro studies demonstrated type I IFN suppressed basophil expansion from bone marrow progenitor cells and survival of mature basophils. Collectively, our work suggests that Ly6Chi monocytes are the first and dominant inflammatory cells reaching AD lesions that negatively regulate type 2 inflammation through the production of type I IFN.

The role of tolerogenic dendritic cells in systematic lupus erythematosus progression and remission

Systematic lupus erythematosus (SLE) is an autoimmune disease reflecting an imbalance between effector and regulatory immune responses. Dendritic cells (DC) are a link between innate and adaptive immunity. Inflammatory DCs (inflDC) can initiate and trigger lymphocyte responses in SLE with over-expression of surface molecules and pro-inflammatory cytokine, including Interferon (IFN) α, Interleukin (IL) 1α, IL-1β, and IL-6, resulting in the overreaction of T helper cells (Th), and B cells immune responses. On the opposite side, tolerogenic DCs (tolDC) express inhibitory interacting surface molecules and repressive mediators, such as IL-10, Transforming growth factor beta (TGF-β), and Indoleamine 2, 3-dioxygenase (IDO), which can maintain self-tolerance in SLE by induction of regulatory T cells (Treg), T cells deletion and anergy. Hence, tolDCs can be a therapeutic candidate for patients with SLE to suppress their systematic inflammation. Recent pre-clinical and clinical studies showed the efficacy of tolDCs therapy in autoimmune diseases. In this review, we provide a wide perspective on the effect of inflDCs in promoting inflammation and the role of tolDC in the suppression of immune cells' overreaction in SLE. Furthermore, we reviewed the finding of clinical trials and experimental studies related to autoimmune diseases, particularly SLE.

NLRP12 is an innate immune checkpoint for repressing IFN signatures and attenuating lupus nephritis progression

Signaling driven by nucleic acid sensors participates in interferonopathy-mediated autoimmune diseases. NLRP12, a pyrin-containing NLR protein, is a negative regulator of innate immune activation and type I interferon (IFN-I) production. Peripheral blood mononuclear cells (PBMCs) derived from systemic lupus erythematosus (SLE) patients expressed lower levels of NLRP12, with an inverse correlation with IFNA expression and high disease activity. NLRP12 expression was transcriptionally suppressed by runt-related transcription factor 1-dependent (RUNX1-dependent) epigenetic regulation under IFN-I treatment, which enhanced a negative feedback loop between low NLRP12 expression and IFN-I production. Reduced NLRP12 protein levels in SLE monocytes was linked to spontaneous activation of innate immune signaling and hyperresponsiveness to nucleic acid stimulations. Pristane-treated Nlrp12-/- mice exhibited augmented inflammation and immune responses; and substantial lymphoid hypertrophy was characterized in NLRP12-deficient lupus-prone mice. NLRP12 deficiency mediated the increase of autoantibody production, intensive glomerular IgG deposition, monocyte recruitment, and the deterioration of kidney function. These were bound in an IFN-I signature-dependent manner in the mouse models. Collectively, we reveal a remarkable link between low NLRP12 expression and lupus progression, which suggests the impact of NLRP12 on homeostasis and immune resilience.

B cell-activating factor (BAFF) from dendritic cells, monocytes and neutrophils is required for B cell maturation and autoantibody production in SLE-like autoimmune disease

Purpose and methods

B cell-activating factor (BAFF) contributes to the pathogenesis of autoimmune diseases including systemic lupus erythematosus (SLE). Although several anti-BAFF Abs and derivatives have been developed for the treatment of SLE, the specific sources of BAFF that sustain autoantibody (auto-Ab) producing cells have not been definitively identified. Using BAFF-RFP reporter mice, we identified major changes in BAFF-producing cells in two mouse spontaneous lupus models (Tlr7 Tg mice and Sle1), and in a pristane-induced lupus (PIL) model.

Results

First, we confirmed that similar to their wildtype Tlr7 Tg and Sle1 mice counterparts, BAFF-RFP Tlr7 Tg mice and BAFF-RFP Sle1 mice had increased BAFF serum levels, which correlated with increases in plasma cells and auto-Ab production. Next, using the RFP reporter, we defined which cells had dysregulated BAFF production. BAFF-producing neutrophils (Nphs), monocytes (MOs), cDCs, T cells and B cells were all expanded in the spleens of BAFF-RFP Tlr7 Tg mice and BAFF-RFP Sle1 mice compared to controls. Furthermore, Ly6C^hi inflammatory MOs and T cells had significantly increased BAFF expression per cell in both spontaneous lupus models, while CD8^- DCs up-regulated BAFF expression only in the Tlr7 Tg mice. Similarly, pristane injection of BAFF-RFP mice induced increases in serum BAFF levels, auto-Abs, and the expansion of BAFF-producing Nphs, MOs, and DCs in both the spleen and peritoneal cavity. BAFF expression in MOs and DCs, in contrast to BAFF from Nphs, was required to maintain homeostatic and pristane-induced systemic BAFF levels and to sustain mature B cell pools in spleens and BMs. Although acting through different mechanisms, Nph, MO and DC sources of BAFF were each required for the development of auto-Abs in PIL mice.

Conclusions

Our findings underscore the importance of considering the relative roles of specific myeloid BAFF sources and B cell niches when developing treatments for SLE and other BAFF-associated autoimmune diseases.

Pathogenesis of Paradoxical Reactions Associated with Targeted Biologic Agents for Inflammatory Skin Diseases

Targeted biologic agents have dramatically changed the therapeutic landscape for immune-mediated inflammatory diseases, particularly in rheumatology and dermatology. Their introduction has resulted in a paradigm shift, i.e., they produce significant clinical improvements in most patients with such diseases. Nevertheless, a variety of adverse reactions associated with these agents have been observed, including so-called paradoxical reactions (PRs), which are a new class of adverse events. PRs involve the de novo development or worsening of immune-mediated inflammatory disease during treatment with a targeted biologic agent that is commonly used to treat the idiopathic counterpart of the drug-induced reaction. In addition, the efficacy of biologic agents targeting individual cytokines and the existence of PRs to them have provided proof that cytokines are key drivers of various immune-mediated inflammatory diseases and helped researchers elucidate the molecular pathways underlying the pathophysiology of these diseases. Here, a comprehensive review of the targeted biologic agents used to treat immune-mediated inflammatory diseases, particularly psoriasis and atopic dermatitis, is provided, with a specific focus on biologic agents that inhibit cytokine signaling involving tumor necrosis factor-α, interleukin (IL)-12/23 (p40), IL-17A (and the IL-17 receptor [R]), IL-23 (p19), and the IL-4Rα, and their associated PRs. The characteristic clinical manifestations and potential immunological mechanisms of the PRs induced by these biologic agents are also reviewed.

Clinical outcomes of COVID-19 patients with rheumatic diseases: a retrospective cohort study and synthesis analysis in Wuhan, China

BACKGROUND

The clinical outcomes of patients with rheumatic diseases infected with COVID-19 were inconsistent characteristics across regions and time periods. We need to revisit and sort out the clinical characteristics of these patients at the beginning of the global COVID-19 epidemic.

METHODS

We collected data from confirmed COVID-19 patients from two military-run field hospitals and classified them into the rheumatic disease group and no rheumatic disease groups, and the latter was further distinguished by ARD and non-ARD. We compared the primary outcome, which we defined as mortality, and the secondary outcome, which we defined as the ICU occupancy rate, the duration of hospitalization and the duration of viral clearance, between the patients with and without rheumatic diseases after PSM. A study-level meta-analysis of four studies was conducted on the mortality of the COVID-19 patients with and without rheumatic diseases.

RESULTS

A total of 4353 COVID-19 patients were included in our cohort study; 91 had rheumatic diseases. The mean age of the entire cohort was 59.37, and 2281 (52.40%) patients were female. The mortalities after PSM were 1.11% and 3.46% in the rheumatic diseases and no rheumatic disease groups, respectively. The ICU occupancy rates after PSM were 2.22% and 4.61% in the rheumatic diseases and no rheumatic disease groups. The duration of hospitalization and viral clearance in the rheumatic disease group were 15.97 and 43.69, respectively; moreover, the same parameters in the no rheumatic diseases after PSM were 15.48 and 45.48. No significant differences were found in either the primary or secondary outcomes. After excluding the gout cases, the results were still similar. However, there was a significant difference between the two groups upon meta-analysis (RR = 1.70, 95% CI 1.35-2.13).

CONCLUSIONS

Rheumatic diseases seemed to aggravate the course of COVID-19 infection. However, the poor outcomes of COVID-19 seemed to be unassociated with rheumatic diseases undergoing an adequate medical intervention.

KEY POINTS

• We compared the outcomes and prognosis of COVID-19 patients in China at the beginning of the outbreak regarding the presence or absence of rheumatic disease patients and made some meaningful conclusions for future outbreaks of similar infectious diseases. • We compared similar recent studies from other countries and explored the changes and differences in patient outcomes associated with COVID-19 as it continued to spread worldwide during the year, providing clinical evidence to further explore the role rheumatic diseases play in COVID-19 patient outcomes. • We provided evidence for the treatment of relevant patients and made rationalized recommendations for treatment strategy.

Abnormal Changes of Monocyte Subsets in Patients With Sjögren’s Syndrome

Background

Recent studies have proven the existence of distinct monocyte subsets, which play a significant role in the development of some rheumatic diseases such as systemic lupus erythematosus (SLE). This study was performed to define the changes of monocyte subsets in patients with Sjögren’s Syndrome (SjS).

Methods

Single cell RNA-sequencing (scRNA-seq) data of monocytes from SjS patients and controls were analyzed. The transcriptomic changes in monocyte subsets between SjS and controls were identified and potential key functional pathways involved in SjS development were also explored.

Results

A total of 11 monocyte subsets were identified in the scRNA-seq analyses of monocytes. A new monocyte subset characterized by higher expression of VNN2 (GPI-80) and S100A12 (Monocyte cluster 3) was identified, and it was increased in SjS patients. Compared with controls, almost all monocyte subsets from SjS patients had increased expression of TNFSF10 (TRAIL). Moreover, interferon (IFN)-related and neutrophil activation-associated pathways were main up-regulated pathways in the monocytes of SjS patients.

Conclusion

This study uncovered the abnormal changes in monocyte subsets and their transcriptomic changes in SjS patients, and identified TNFSF10 ^high/+ monocytes as a potential key player in SjS pathogenesis and a promising target for SjS treatment.

Characteristics of immune induction by transcutaneous vaccination using dissolving microneedle patches in mice

Transcutaneous immunization (TCI) is an appealing vaccination method. Compared with conventional injectable immunization, TCI is easier and less painful. We previously developed a dissolving microneedle (MN) patch and demonstrated that TCI using MN patches demonstrates high vaccination efficacy without adverse events in humans. In this study, we investigated the immune induction mechanism of TCI using our MN patch, focusing on inflammatory responses in the skin and on the dynamics, activation, and differentiation of various immunocompetent cells in draining lymph nodes (dLNs). We demonstrate that inflammatory cytokines such as IL-6 and TNF-α increased in the skin at an early stage after MN patch application, inducing the infiltration of macrophages and neutrophils and promoting the activation and migration of skin-resident antigen-presenting cells (Langerhans and Langerin^- dermal dendritic cells) to dLNs. Moreover, the activated antigen-presenting cells reaching the dLNs enhanced the differentiation of T (T_eff, T_em, and T_cm) and B (plasma and memory) cells. This may contribute to the efficient antigen-specific antibody production induced by TCI using MN patches. We believe that our findings reveal a part of the immune induction mechanism by TCI and provide useful information for the development and improvement of TCI formulations based on the immune induction mechanism.