Hypoxia-inducible factor-1α regulates the interleukin-6 production by B cells in rheumatoid arthritis.

Objectives: Rheumatoid arthritis (RA) is a disease characterised by bone destruction and systemic inflammation, and interleukin-6 (IL-6) is a therapeutic target for treating it. The study aimed at investigating the sources of IL-6 and the influence of hypoxia-inducible factor-1α (HIF-1α) on IL-6 production by B cells in RA patients. Methods: The phenotype of IL-6-producing cells in the peripheral blood of RA patients was analysed using flow cytometry. Bioinformatics, real-time polymerase chain reaction, Western blot and immunofluorescence staining were used to determine the IL-6 production and HIF-1α levels in B cells. A dual-luciferase reporter assay and chromatin immunoprecipitation were used to investigate the regulatory role of HIF-1α on IL-6 production in human and mouse B cells. Results: Our findings revealed that B cells are major sources of IL-6 in the peripheral blood of RA patients, with the proportion of IL-6-producing B cells significantly correlated with RA disease activity. The CD27-IgD+ naïve B cell subset was identified as the typical IL-6-producing subset in RA patients. Both HIF-1α and IL-6 were co-expressed by B cells in the peripheral blood and synovium of RA patients, and HIF-1α was found to directly bind to the IL6 promoter and enhance its transcription. Conclusion: This study highlights the role of B cells in producing IL-6 and the regulation of this production by HIF-1α in patients with RA. Targeting HIF-1α might provide a new therapeutic strategy for treating RA.

T follicular helper 17 (Tfh17) cells are superior for immunological memory maintenance.

A defining feature of successful vaccination is the ability to induce long-lived antigen-specific memory cells. T follicular helper (Tfh) cells specialize in providing help to B cells in mounting protective humoral immunity in infection and after vaccination. Memory Tfh cells that retain the CXCR5 expression can confer protection through enhancing humoral response upon antigen re-exposure but how they are maintained is poorly understood. CXCR5+ memory Tfh cells in human blood are divided into Tfh1, Tfh2, and Tfh17 cells by the expression of chemokine receptors CXCR3 and CCR6 associated with Th1 and Th17, respectively. Here, we developed a new method to induce Tfh1, Tfh2, and Tfh17-like (iTfh1, iTfh2, and iTfh17) mouse cells in vitro. Although all three iTfh subsets efficiently support antibody responses in recipient mice with immediate immunization, iTfh17 cells are superior to iTfh1 and iTfh2 cells in supporting antibody response to a later immunization after extended resting in vivo to mimic memory maintenance. Notably, the counterpart human Tfh17 cells are selectively enriched in CCR7+ central memory Tfh cells with survival and proliferative advantages. Furthermore, the analysis of multiple human cohorts that received different vaccines for HBV, influenza virus, tetanus toxin or measles revealed that vaccine-specific Tfh17 cells outcompete Tfh1 or Tfh2 cells for the persistence in memory phase. Therefore, the complementary mouse and human results showing the advantage of Tfh17 cells in maintenance and memory function supports the notion that Tfh17-induced immunization might be preferable in vaccine development to confer long-term protection.

Supranutritional selenium suppresses ROS-induced generation of RANKL-expressing osteoclastogenic CD4+ T cells and ameliorates rheumatoid arthritis.

OBJECTIVE: The benefit of Se supplementation in rheumatoid arthritis (RA) has been tested in clinical trials, but results remain inconclusive. The objective of this study was to specifically investigate the potential benefit of supranutritional Se by examining human samples from an area with supranutritional Se intake and testing a mouse model of RA. METHODS: Peripheral blood mononuclear cells (PBMCs) from RA patients (N = 57) and healthy controls (HC, N = 71) from an area of supranutritional Se intake (Enshi, Hubei, China) were analysed by flow cytometry. Serum cytokine and Se levels were measured by cytometric beads array (CBA) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. With sufficient or supranutritional selenium intake, mice were induced with collagen-induced arthritis (CIA) and examined for disease activity and immunopathology. The influence of Se supplementation in the generation of RANKL-expressing osteoclastogenic CD4+ T cells was investigated by in vitro assays. RESULTS: In Enshi city, HC showed the above-normal concentrations of serum Se concentrations while RA patients were enriched in the normal range (70-150 ng mL-1) or below. RA patients with higher Se levels demonstrated milder disease and lower levels of C-reactive protein, IL-6, RANKL and Th17 cells. In the mouse CIA model, supranutritional Se supplementation delayed disease onset, ameliorated joint pathology and reduced CD4+CD44+RANKL+ T cells. Se supplementation could suppress RANKL expression in cultured mouse Th17 cells. CONCLUSION: Supranutritional Se suppresses RANKL-expressing osteoclastogenic CD4+ T cells and could be beneficial to RA, which warrants formal testing in randomised clinical trials.

Sustained low-dose interleukin-2 therapy alleviates pathogenic humoral immunity via elevating the Tfr/Tfh ratio in lupus.

OBJECTIVES: Low-dose interleukin-2 (IL-2) has shown promising clinical benefits in the treatment of systemic lupus erythematosus (SLE), but how this therapy alleviates pathogenic humoral immunity remains not well understood. The dilemma is that IL-2 can suppress both follicular helper and regulatory T (Tfh and Tfr) cells, which counteract each other in regulating autoantibody production. METHODS: Female NZB/W F1 mice received recombinant human IL-2 (3 × 104 IU/dose) in three treatment regimens: (1) short, daily for 7 days; (2) medium, daily for 14 days, and (3) long, every second day for 28 days. Tfh (Foxp3-CXCR5+Bcl6+), Tfr (Foxp3+CXCR5+Bcl6+), germinal centre (GC, B220+GL-7+Fas+) and antibody-secreting cell (ASC, B220-CD138+TACI+) were analysed by flow cytometry. Serum anti-dsDNA level was determined by ELISA. Kidney pathology was evaluated by H&E and immunofluorescence staining. Circulating Tfh and Tfr cells in SLE patients treated with low-dose IL-2 from a previous clinical trial (NCT02084238) was analysed. RESULTS: Low-dose IL-2 treatment consistently increased Tfr/Tfh ratio in mice and SLE patients, because of a stronger suppression on Tfh cells than Tfr cells. Three treatment regimens revealed distinct immunological features. Tfh suppression was observed in all regimens, but Tfr suppression and GC reduction were recorded in just medium and long regimens. Only the long treatment regimen resulted in inhibited ASC differentiation in spleen, which was accompanied by reduced anti-dsDNA titres and ameliorated kidney pathology. CONCLUSION: Low-dose IL-2 therapy increases the Tfr/Tfh ratio, and a less frequent and prolonged treatment can alleviate pathogenic humoral immunity and improve renal function.

Bile Acids Impair Vaccine Response in Children With Biliary Atresia.

Background: Vaccination is the best way to protect children under 5 years from death or disability. Children with biliary atresia (BA), which is the most common pediatric cholestatic end-stage liver disease (PELD), are more vulnerable to infectious diseases. However, the vaccination coverage and factors modulating vaccine responses in children with BA are largely unknown. Methods: In this study, 288 children (median age: 7 months) diagnosed with BA before liver transplantation were enrolled for the evaluation of vaccination status and the factors affecting the immune response to the hepatitis B (HBV) vaccine. Moreover, 49 BA children (median age: 4 months) were enrolled for flow cytometric analysis of CD4+ T cells and CD19+ B cell subsets and correlations with serum bile acid levels. Results: Generally, these children had very low routine vaccination rates for the meningococcal serogroup AC (Men AC) (41.2%), measles-mumps-rubella (MMR) (31.3%), poliomyelitis (Polio) (25.3%), hepatitis A (HAV) (25.0%), Japanese encephalitis (JE) (15.0%), diphtheria-tetanus-pertussis (DTP) (14.2%), meningococcal serogroup A (Men A) (13.5%) and varicella (VAR) (10.8%) vaccines, but not for the HBV (96.2%) and bacillus Calmette-Guérin (BCG) (84.7%) vaccines. Remarkably, 19.8% (57/288) of the patients had HBV infection. Out of 220 patients vaccinated for HBV, 113 (51.4%), 85 (38.6%) and 22 (10%) had one, two or three doses of the HBV vaccine, respectively. Furthermore, logistic regression analysis revealed that the bile acid level was an independent factor associated with poor HBV vaccine response (p = 0.03; OR = 0.394; 95% CI = 0.170-0.969). Immunophenotyping showed that bile acids were only negatively correlated with the CD19+CD27+IgG+ post-class-switched memory B cell ratio (p = 0.01). Conclusion: This study reveals the overall vaccination rates of routine vaccines in Chinese BA children are very low and the poor HBV vaccine responses are associated with bile acids, possibly via the inhibition of CD19+CD27+IgG+ post-class-switched memory B cell response. Clinical Trial Registration: http://www.chictr.org.cn, identifier ChiCTR1800019165.

The metabolic hormone leptin promotes the function of TFH cells and supports vaccine responses.

Follicular helper T (TFH) cells control antibody responses by supporting antibody affinity maturation and memory formation. Inadequate TFH function has been found in individuals with ineffective responses to vaccines, but the mechanism underlying TFH regulation in vaccination is not understood. Here, we report that lower serum levels of the metabolic hormone leptin associate with reduced vaccine responses to influenza or hepatitis B virus vaccines in healthy populations. Leptin promotes mouse and human TFH differentiation and IL-21 production via STAT3 and mTOR pathways. Leptin receptor deficiency impairs TFH generation and antibody responses in immunisation and infection. Similarly, leptin deficiency induced by fasting reduces influenza vaccination-mediated protection for the subsequent infection challenge, which is mostly rescued by leptin replacement. Our results identify leptin as a regulator of TFH cell differentiation and function and indicate low levels of leptin as a risk factor for vaccine failure.

Corrigendum: Signal Transducer and Activator of Transcription 3 Hyperactivation Associates With Follicular Helper T Cell Differentiation and Disease Activity in Rheumatoid Arthritis.

[This corrects the article DOI: 10.3389/fimmu.2018.01226.].

Signal Transducer and Activator of Transcription 3 Hyperactivation Associates With Follicular Helper T Cell Differentiation and Disease Activity in Rheumatoid Arthritis.

Follicular helper T (Tfh) cells are the specialized CD4+ T cell subset that supports B cells to produce high-affinity antibodies and generate humoral memory. Not only is the function of Tfh cells instrumental to mount protect antibodies but also to support autoantibody production and promote systemic inflammation in autoimmune diseases. However, it remains unclear how the activation of Tfh cells is driven in autoimmune diseases. Here, we report that in patients with rheumatoid arthritis (RA), excessive generation of CXCR5+PD-1+ memory Tfh cells was observed and the frequency of memory Tfh cells correlated with disease activity score calculator for RA (DAS28). The differentiation of Tfh cells is dependent on signal transducer and activator of transcription 3 (STAT3), the key transcription factor downstream of cytokine signal pathways. A drastic increase of phosphorylated STAT3 (pSTAT3) in CD4+ T cells were detected in RA patients who also produced larger amounts of STAT3-stimulating cytokines, including IL-6, IL-21, IL-10, and leptin than those of healthy controls. Importantly, the phosphorylation status of STAT3 in CD4+ T cells positively correlated with the plasma concentration of IL-6 and the frequency of memory Tfh cells. This study reveals an IL-6-pSTAT3-Tfh immunoregulatory axis in the pathogenesis of RA and reinforces its candidature as biomarkers and targets for diagnosis and therapy.