The emergence of circulating activated autoreactive desmoglein 3-specific follicular regulatory T cells is associated with long-term efficacy of rituximab in patients with pemphigus vulgaris.

BACKGROUND: Pemphigus vulgaris (PV) is characterized by autoantibodies targeting keratinocyte adhesion proteins desmoglein (Dsg) 1 and 3, and by the human leukocyte antigen (HLA) predisposition allele HLA-DRB1*0402. Treatment using rituximab (RTX) combined with short-term corticosteroids (CS) allows disease control and long-lasting remission. OBJECTIVES: The principal aim of this study was to evaluate the impact of RTX on the circulating subpopulations of Dsg3-specific T lymphocytes that specifically regulate B-cell responses: follicular helper T (Tfh) and follicular regulatory T (Tfr) lymphocytes. METHODS: Using the HLA-DRB1*0402 tetramer loaded with the Dsg3 immunodominant peptide, we used flow cytometry to analyse the frequency, polarization and activation status of blood Dsg3-specific follicular T-cell populations at baseline, month (M) 6 and long-term follow-up (M60-90) from patients with PV. RESULTS: At baseline, we observed a predominance of Tfh1* and Tfh17 subsets and an underrepresentation of the Tfh2 subset among autoreactive Dsg3-specific Tfh cells compared with nonautoreactive Tfh cells. RTX treatment induced a decrease of autoreactive Tfh cells with no effect on their polarization during follow-up. In parallel, we observed the emergence of a Dsg3-specific Tfr subpopulation with a significant overexpression of the surface activation markers PD1, ICOS and CD25 that was not observed at the surface of autoreactive Tfh and nonautoreactive Tfr cells of the same patients with PV. In contrast, very few Dsg3-specific Tfr cells were observed in patients with PV who were treated with CS alone. CONCLUSIONS: Here we show that the emergence of circulating autoreactive Dsg3-specific Tfr cells is associated with the long-term efficacy of RTX in patients with PV.

Pemphigus vulgaris (PV) is an autoimmune disease mediated by pathogenic antibodies directed against the body's own tissues (called autoantibodies). In this condition, autoantibodies bind to and inhibit a protein called desmoglein 3 (Dsg3), which is responsible for the adhesion of keratinocytes (cells that make up the superficial layers of the skin and mucous membranes). As a result, PV causes painful blistering. People with PV are commonly treated with low doses of oral corticosteroids (prednisone) and rituximab (administered via infusions), which have significantly improved patient outcomes. Rituximab temporarily (for 6­9 months) depletes B lymphocytes, which are immune cells that differentiate into cells producing anti-Dsg3 antibodies. While autoimmune diseases can be lifelong, this study looked at why some people achieve long-lasting remissions without ongoing treatment, even after the return of B lymphocytes. We analysed anti-Dsg3 follicular T cells, which regulate B-cell differentiation. Among these, we observed the emergence of regulatory (or inhibiting) T cells over time following treatment, accompanied by a decrease in conventional (or activating) follicular T cells. We also found that these autoimmune follicular regulatory T cells were more activated compared with conventional follicular T cells or other T cells not directed against the Dsg3 protein. Overall, our findings suggest that the emergence of these follicular regulatory T cells may be responsible for the sustained remission observed in some people with PV and could be promoted by the use of rituximab.

Enkephalin-mediated modulation of basal somatic sensitivity by regulatory T cells in mice.

CD4+CD25+Foxp3+ regulatory T cells (Treg) have been implicated in pain modulation in various inflammatory conditions. However, whether Treg cells hamper pain at steady state and by which mechanism is still unclear. From a meta-analysis of the transcriptomes of murine Treg and conventional T cells (Tconv), we observe that the proenkephalin gene (Penk), encoding the precursor of analgesic opioid peptides, ranks among the top 25 genes most enriched in Treg cells. We then present various evidence suggesting that Penk is regulated in part by members of the Tumor Necrosis Factor Receptor (TNFR) family and the transcription factor Basic leucine zipper transcription faatf-like (BATF). Using mice in which the promoter activity of Penk can be tracked with a fluorescent reporter, we also show that Penk expression is mostly detected in Treg and activated Tconv in non-inflammatory conditions in the colon and skin. Functionally, Treg cells proficient or deficient for Penk suppress equally well the proliferation of effector T cells in vitro and autoimmune colitis in vivo. In contrast, inducible ablation of Penk in Treg leads to heat hyperalgesia in both male and female mice. Overall, our results indicate that Treg might play a key role at modulating basal somatic sensitivity in mice through the production of analgesic opioid peptides.

Ageing of T-dependent B cell responses.

The human immune system is in continuous interaction with environmental factors (pathogens, exercise, stress, pollutants, diet, vaccines, and therapeutics) that condition its efficiency by promoting or moderating multiple immune mechanisms. While the deleterious impact of external factors can be avoided or limited, the immune system itself grows weaker with age. Immune cells persist in the elderly, and the observed decline of cellular immunity is related to cellular senescence. Immunosenescence, which affects both T and B cells, erodes lymphocyte-dependent responses to vaccines and pathogens. Germinal centers (GCs), the organized lymphoid structures where B cells engage in affinity maturation, are regulated by follicular helper (Tfh) and follicular regulatory (Tfr) T cells, the major T cell components of GCs. This review discusses how age-related changes affect Tfh and Tfr cells as key components of B cell immunity, and how they ultimately shape the response of the ageing immune system to vaccines and infectious challenges.

Ageing promotes early T follicular helper cell differentiation by modulating expression of RBPJ.

Ageing profoundly changes our immune system and is thought to be a driving factor in the morbidity and mortality associated with infectious disease in older people. We have previously shown that the impaired immunity to vaccination that occurs in aged individuals is partly attributed to the effect of age on T follicular helper (Tfh) cell formation. In this study, we examined how age intrinsically affects Tfh cell formation in both mice and humans. We show increased formation of Tfh precursors (pre-Tfh) but no associated increase in germinal centre (GC)-Tfh cells in aged mice, suggesting age-driven promotion of only early Tfh cell differentiation. Mechanistically, we show that ageing alters TCR signalling which drives expression of the Notch-associated transcription factor, RBPJ. Genetic or chemical modulation of RBPJ or Notch rescues this age-associated early Tfh cell differentiation, and increased intrinsic Notch activity recapitulates this phenomenon in younger mice. Our data offer mechanistic insight into the age-induced changes in T-cell activation that affects the differentiation and ultimately the function of effector T cells.

Evidence for tmTNF reverse signaling in vivo: Implications for an arginase-1-mediated therapeutic effect of TNF inhibitors during inflammation.

In order to ascertain the significance of transmembrane tumor necrosis factor (tmTNF) reverse signaling in vivo, we generated a triple transgenic mouse model (3TG, TNFR1-/-, TNFR2-/-, and tmTNFKI/KI) in which all canonical tumor necrosis factor (TNF) signaling was abolished. In bone-marrow-derived macrophages harvested from these mice, various anti-TNF biologics induced the expression of genes characteristic of alternative macrophages and also inhibited the expression of pro-inflammatory cytokines mainly through the upregulation of arginase-1. Injections of TNF inhibitors during arthritis increased pro-resolutive markers in bone marrow precursors and joint cells leading to a decrease in arthritis score. These results demonstrate that the binding of anti-TNF biologics to tmTNF results in decreased arthritis severity. Collectively, our data provide evidence for the significance of tmTNF reverse signaling in the modulation of arthritis. They suggest a complementary interpretation of anti-TNF biologics effects in the treatment of inflammatory diseases and pave the way to studies focused on new arginase-1-dependent therapeutic targets.