TL1A increases expression of CD25, LFA-1, CD134 and CD154, and induces IL-22 and GM-CSF production from effector CD4 T-cells

TL1A and IL-18 synergy promotes GM-CSF-dependent thymic granulopoiesis in mice

Acute systemic inflammation critically alters the function of the immune system, often promoting myelopoiesis at the expense of lymphopoiesis. In the thymus, systemic inflammation results in acute thymic atrophy and, consequently, impaired T-lymphopoiesis. The mechanism by which systemic inflammation impacts the thymus beyond suppressing T-cell development is still unclear. Here, we describe how the synergism between TL1A and IL-18 suppresses T-lymphopoiesis to promote thymic myelopoiesis. The protein levels of these two cytokines were elevated in the thymus during viral-induced thymus atrophy infection with murine cytomegalovirus (MCMV) or pneumonia virus of mice (PVM). In vivo administration of TL1A and IL-18 induced acute thymic atrophy, while thymic neutrophils expanded. Fate mapping with Ms4a3-Cre mice demonstrated that thymic neutrophils emerge from thymic granulocyte-monocyte progenitors (GMPs), while Rag1-Cre fate mapping revealed a common developmental path with lymphocytes. These effects could be modeled ex vivo using neonatal thymic organ cultures (NTOCs), where TL1A and IL-18 synergistically enhanced neutrophil production and egress. NOTCH blockade by the LY411575 inhibitor increased the number of neutrophils in the culture, indicating that NOTCH restricted steady-state thymic granulopoiesis. To promote myelopoiesis, TL1A, and IL-18 synergistically increased GM-CSF levels in the NTOC, which was mainly produced by thymic ILC1s. In support, TL1A- and IL-18-induced granulopoiesis was completely prevented in NTOCs derived from Csf2rb-/- mice and by GM-CSFR antibody blockade, revealing that GM-CSF is the essential factor driving thymic granulopoiesis. Taken together, our findings reveal that TL1A and IL-18 synergism induce acute thymus atrophy while  promoting extramedullary thymic granulopoiesis in a NOTCH and GM-CSF-controlled manner.

Clinical Staphylococcus aureus inhibits human T-cell activity through interaction with the PD-1 receptor

IMPORTANCE

Therapies that target and aid the host immune defense to repel cancer cells or invading pathogens are rapidly emerging. Antibiotic resistance is among the largest threats to human health globally. Staphylococcus aureus (S. aureus) is the most common bacterial infection, and it poses a challenge to the healthcare system due to its significant ability to develop resistance toward current available therapies. In long-term infections, S. aureus further adapt to avoid clearance by the host immune defense. In this study, we discover a new interaction that allows S. aureus to avoid elimination by the immune system, which likely supports its persistence in the host. Moreover, we find that blocking the specific receptor (PD-1) using antibodies significantly relieves the S. aureus-imposed inhibition. Our findings suggest that therapeutically targeting PD-1 is a possible future strategy for treating certain antibiotic-resistant staphylococcal infections.

Elevated levels of TL1A are associated with disease activity in patients with systemic sclerosis

TL1A is a member of the TNF superfamily. It performs significantly in the pathogenesis of rheumatic and autoimmune diseases partly through regulating the Th17 pathway. The clinical implication of circulating TL1A in patients with systemic sclerosis (SSc) remains unclear, and correlation between TL1A and Th17-related cytokines in the pathogenesis of SSc needs to be discussed. We measured serum levels of TL1A and Th17-related cytokines by ELISA in 47 patients with SSc, 56 patients with SLE, and 53 healthy subjects, and investigated association of these cytokines with clinical manifestations and laboratory variables. TL1A in relation to Th17-related cytokines were examined. In addition, the transcript level of TL1A in peripheral blood mononuclear cells (PBMCs) was determined by real-time reverse transcription polymerase chain reaction (real-time PCR). Serum TL1A levels were higher in patients with SSc than in healthy controls (P = 0.001), but were lower compared with SLE patients (P = 0.004). Diffuse cutaneous SSc or limited cutaneous SSc patients reported elevated expression of TL1A than those in healthy controls (P = 0.002, P = 0.007). Patients with active disease showed significantly higher expression of TL1A when compared with less active disease (P = 0.014). SSc patients with arthritis, elevated IgG titer, ESR >30 mm/h, and CRP >5 mg/l displayed elevated expression of TL1A, respectively. Serum levels of IL-17 and IL-21 were increased in SSc patients compared with healthy controls and positively related to TL1A levels (r _s = 0.373, P = 0.010; r _s = 0.370, P = 0.011, respectively). Moreover, TL1A mRNA expression in PBMCs was significantly higher in patients with SSc compared with healthy controls (P < 0.001). TL1A may play a role in the development of SSc.

The TNF-family cytokine TL1A: from lymphocyte costimulator to disease co-conspirator

Originally described in 2002 as a T cell-costimulatory cytokine, the tumor necrosis factor family member TNF-like factor 1A (TL1A), encoded by the TNFSF15 gene, has since been found to affect multiple cell lineages through its receptor, death receptor 3 (DR3, encoded by TNFRSF25) with distinct cell-type effects. Genetic deficiency or blockade of TL1A-DR3 has defined a number of disease states that depend on this cytokine-receptor pair, whereas excess TL1A leads to allergic gastrointestinal inflammation through stimulation of group 2 innate lymphoid cells. Noncoding variants in the TL1A locus are associated with susceptibility to inflammatory bowel disease and leprosy, predicting that the level of TL1A expression may influence host defense and the development of autoimmune and inflammatory diseases.

The TL1A/DR3/DcR3 pathway in autoimmune rheumatic diseases

IMPORTANCE

TNF-like cytokine 1A (TL1A) and its receptors, death receptor 3 (DR3) and decoy receptor 3 (DcR3) are members of the TNF and TNF receptor superfamilies of proteins, respectively. They constitute a cytokine system that actively interferes with the regulation of immune responses and may participate in the pathogenesis of autoimmune diseases.

OBJECTIVES

This review aims to present the current knowledge on the role of the TL1A/DR3/DcR3 system in the pathophysiology of autoimmune rheumatic diseases, with a focus on rheumatoid arthritis (RA).

METHODS

An extensive literature search was performed in the PubMed database using the following keywords: TL1A, death receptor 3, DR3, decoy receptor 3, DcR3, TNFSF15, TNFRSF25, and TNFSF6B. Studies were assessed and selected in view of their relevance to autoimmune rheumatic diseases.

CONCLUSION

The TL1A/DR3/DcR3 axis is a novel immune pathway that participates in the pathogenesis of a variety of autoimmune rheumatic diseases. These molecules may be promising therapeutic targets for inflammatory arthritis.