Th17 cells generated in the absence of TGF-β induce experimental allergic encephalitis upon adoptive transfer

TGF-β1 suppresses the T-cell response in teleost fish by initiating Smad3- and Foxp3-mediated transcriptional networks

Transforming growth factor-β1 (TGF-β1) can suppress the activation, proliferation, and function of many T-cell subsets, protecting organisms from inflammatory and autoimmune disease caused by an overexuberant immune response. However, whether and how TGF-β1 regulates T-cell immunity in early vertebrates remain unknown. Here, using a Nile tilapia (Oreochromis niloticus) model, we investigated suppression of the T-cell response by TGF-β1 in teleost species. Tilapia encodes an evolutionarily conserved TGF-β1, the expression of which in lymphocytes is significantly induced during the immune response following Edwardsiella piscicida infection. Once activated, tilapia T cells increase TGF-β1 production, which in turn suppresses proinflammatory cytokine expression and inhibits T-cell activation. Notably, we found administration of TGF-β1 cripples the proliferation of tilapia T cells, reduces the potential capacity of Th1/2 differentiation, and impairs the cytotoxic function, rendering the fish more vulnerable to bacterial infection. Mechanistically, TGF-β1 initiates the TGF-βR/Smad signaling pathway and triggers the phosphorylation and nuclear translocation of Smad2/3. Smad3 subsequently interacts with several transcriptional partners to repress transcription of cytokines IL-2 and IFN-γ but promote transcription of immune checkpoint regulator CTLA4 and transcription factor Foxp3. Furthermore, TGF-β1/Smad signaling further utilizes Foxp3 to achieve the cascade regulation of these T-cell genes. Taken together, our findings reveal a detailed mechanism by which TGF-β1 suppresses the T cell-based immunity in Nile tilapia and support the notion that TGF-β1 had already been employed to inhibit the T-cell response early in vertebrate evolution, thus providing novel insights into the evolution of the adaptive immune system.

The correlation between the Th17/Treg cell balance and bone health

With the ageing of the world population, osteoporosis has become a problem affecting quality of life. According to the traditional view, the causes of osteoporosis mainly include endocrine disorders, metabolic disorders and mechanical factors. However, in recent years, the immune system and immune factors have been shown to play important roles in the occurrence and development of osteoporosis. Among these components, regulatory T (Treg) cells and T helper 17 (Th17) cells are crucial for maintaining bone homeostasis, especially osteoclast differentiation. Treg cells and Th17 cells originate from the same precursor cells, and their differentiation requires involvement of the TGF-β regulated signalling pathway. Treg cells and Th17 cells have opposite functions. Treg cells inhibit the differentiation of osteoclasts in vivo and in vitro, while Th17 cells promote the differentiation of osteoclasts. Therefore, understanding the balance between Treg cells and Th17 cells is anticipated to provide a new idea for the development of novel treatments for osteoporosis.

Metabolism Controls the Balance of Th17/T-Regulatory Cells

Accumulating evidence indicates that metabolism reprogramming is critically important to T cell differentiation, and manipulating metabolic pathways in T cells can shape their fate and function. During T cell differentiation, metabolism provides T cells with energy as well as precursors for various biological processes. Some key metabolic reactions, such as glycolysis, oxidative phosphorylation and fatty acid oxidation, are also considered to play important roles in T cell activation and differentiation. In this review, we will explain why cellular metabolism is important for the Th17/T-regulatory (Treg) cell balance and how metabolism reprogramming impacts this balance. Moreover, we will also discuss some important metabolic sensors, such as mammalian target of rapamycin, AMP-activated protein kinase, and some nuclear receptors. In addition, we will review specific small molecular compounds, which can shift the Th17/Treg cell balance and, therefore, have promising therapeutic roles. Finally, potential methods of manipulating Th17 cell metabolism for treating Th17-associated diseases will be discussed.

Leukotriene C(4) prevents the complete maturation of murine dendritic cells and modifies interleukin-12/interleukin-23 balance

Leukotriene C(4) is an important mediator in the development of inflammatory reactions and ischaemia. Previous studies have shown that leukotriene C(4) is able to modulate the function of dendritic cells (DCs) and induce their chemotaxis from skin to lymph node. In this study, we decided to evaluate the modulation exerted by leukotriene C(4) on DCs, depending on their status of activation. We showed for the first time that leukotriene C(4) stimulates endocytosis both in immature and lipopolysaccharide (LPS) -activated DCs. Moreover, it suppressed the interleukin-12p70 (IL-12p70) release, but induces the secretion of IL-23 by DCs activated with LPS and promotes the expansion of T helper type 17 (Th17) lymphocytes. Furthermore, blocking the release of IL-23 reduced the percentages of CD4(+) T cells producing IL-17 in a mixed lymphocyte reaction. Ours results suggest that leukotriene C(4) interferes with the complete maturation of inflammatory DCs in terms of phenotype and antigen uptake, while favouring the release of IL-23, the main cytokine involved in the maintenance of the Th17 profile.