Staphylococcal enterotoxin B (SEB) activates TCR- and CD28-mediated inflammatory signals in the absence of MHC class II molecules

The inflammatory activity of staphylococcal enterotoxin B (SEB) relies on its capacity to trigger polyclonal T‐cell activation by binding both T‐cell receptor (TCR) and costimulatory receptor CD28 on T cells and MHC class II and B7 molecules on antigen presenting cells (APC). Previous studies highlighted that SEB may bind TCR and CD28 molecules independently of MHC class II, yet the relative contribution of these interactions to the pro‐inflammatory function of SEB remained unclear. Here, we show that binding to MHC class II is dispensable for the inflammatory activity of SEB, whereas binding to TCR, CD28 and B7 molecules is pivotal, in both human primary T cells and Jurkat T cell lines. In particular, our finding is that binding of SEB to B7 molecules suffices to trigger both TCR‐ and CD28‐mediated inflammatory signalling. We also provide evidence that, by strengthening the interaction between CD28 and B7, SEB favours the recruitment of the TCR into the immunological synapse, thus inducing lethal inflammatory signallin

CD28 individual signaling up-regulates IL-22 expression and IL-22-mediated effector functions in human T lymphocytes

IL‐22 is a member of the IL‐10 cytokine family involved in host protection against extracellular pathogens, by promoting epithelial cell regeneration and barrier functions. Dysregulation of IL‐22 production has also frequently been observed in acute respiratory distress syndrome (ARDS) and several chronic inflammatory and autoimmune diseases. We have previously described that human CD28, a crucial co‐stimulatory receptor necessary for full T cell activation, is also able to act as a TCR independent signalling receptor and to induce the expression of IL‐17A and inflammatory cytokines related to Th17 cells, which together with Th22 cells represent the main cellular source of IL‐22. Here we characterized the role of CD28 autonomous signalling in regulating IL‐22 expression in human CD4+ T cells. We show that CD28 stimulation in the absence of TCR strongly up‐regulates IL‐22 gene expression and secretion. As recently observed for IL‐17A, we also found that CD28‐mediated regulation of IL‐22 transcription requires the cooperative activities of both IL‐6‐activated STAT3 and RelA/NF‐κ transcription factors. CD28‐mediated IL‐22 production also promotes the barrier functions of epithelial cells by inducing mucin and metalloproteases expression. Finally, by using specific inhibitory drugs, we also identified CD28‐associated class 1A phosphatidylinositol 3‐kinase (PI3K) as a pivotal mediator of CD28‐mediated IL‐22 expression and IL‐ 22‐dependent epithelial cell barrier functions

CD28 autonomous signaling orchestrates IL-22 expression and IL-22-regulated epithelial barrier functions in human T lymphocytes

IL-22 is a member of the IL-10 cytokine family involved in host protection against extracellular pathogens, by promoting epithelial cell regeneration and barrier functions. Dysregulation of IL-22 production has also frequently been observed in acute respiratory distress syndrome (ARDS) and several chronic inflammatory and autoimmune diseases. We have previously described that human CD28, a crucial co-stimulatory receptor necessary for full T cell activation, is also able to act as a TCR independent signaling receptor and to induce the expression of IL-17A and inflammatory cytokines related to Th17 cells, which together with Th22 cells represent the main cellular source of IL-22. Here we characterized the role of CD28 autonomous signaling in regulating IL-22 expression in human CD4+ T cells. We show that CD28 stimulation in the absence of TCR strongly up-regulates IL-22 gene expression and secretion. As recently observed for IL-17A, we also found that CD28-mediated regulation of IL-22 transcription requires the cooperative activities of both IL-6-activated STAT3 and RelA/NF-κB transcription factors. CD28-mediated IL-22 production also promotes the barrier functions of epithelial cells by inducing mucin and metalloproteases expression. Finally, by using specific inhibitory drugs, we also identified CD28-associated class 1A phosphatidylinositol 3-kinase (PI3K) as a pivotal mediator of CD28-mediated IL-22 expression and IL-22–dependent epithelial cell barrier functions

Astrocytes and inflammatory T Helper Cells: a dangerous liaison in Multiple Sclerosis

Multiple Sclerosis (MS) is a neurodegenerative autoimmune disorder of the central nervous system (CNS) characterized by the recruitment of self-reactive T lymphocytes, mainly inflammatory T helper (Th) cell subsets. Once recruited within the CNS, inflammatory Th cells produce several inflammatory cytokines and chemokines that activate resident glial cells, thus contributing to the breakdown of blood-brain barrier (BBB), demyelination and axonal loss. Astrocytes are recognized as key players of MS immunopathology, which respond to Th cell-defining cytokines by acquiring a reactive phenotype that amplify neuroinflammation into the CNS and contribute to MS progression. In this review, we summarize current knowledge of the astrocytic changes and behaviour in both MS and experimental autoimmune encephalomyelitis (EAE), and the contribution of pathogenic Th1, Th17 and Th1-like Th17 cell subsets, and CD8+ T cells to the morphological and functional modifications occurring in astrocytes and their pathological outcomes

CD28 and associated class 1A P13K regulates the glycolytic metabolic program associated to pro-inflammatory T cell responses in Multiple Sclerosis

Introduction CD28 is a crucial costimulatory receptor necessary for full T cell activation. One important contribution of CD28 to T cell activation relies on its ability to regulate T cell metabolism by enhancing nutrient uptake, aerobic glycolysis and anabolic pathways. Indeed, CD28 binds class 1A PI3K that in turn recruits and activates the PDK1/Akt/mTOR pathway. We have recently found that CD28 stimulation strongly up-regulates the expression of cytokines related to the Th17 cell phenotype in relapsing-remitting multiple sclerosis (RRMS) patients. Objectives The aim of this work was to characterize the role of CD28 and associated class 1A PI3K in the modulation of the metabolic programs regulating pro-inflammatory Th17 cell responses in RRMS. Patients & methods. 30 patients with a clinically defined MS according to the McDonald criteria and a clinically RRMS were enrolled from S. Camillo Hospital, (Rome, Italy). 30 age-/gender-matched healthy donor (HD) buffy coats from the blood bank of Sapienza University (Rome, Italy) with no previous history of neurological or autoimmune diseases were used as controls. CD4+ T cells isolated from the peripheral blood of HDs or RRMS patients were stimulated with agonistic anti-CD28 antibodies and changes in cellular metabolism (Seahorse technology), surface expression of activation markers and the glucose transporter 1 (Glut -1) (Flow cytometry) as well as the expression of pro-inflammatory cytokines and metabolic enzymes (Real-time PCR, ELISA, western blotting) were analysed. Results: CD28 stimulation up-regulated glycolysis without significantly affecting mitochondrial oxidative phosphorylation in CD4+ cells from RRMS patients. The analysis of the major enzymes regulating the glycolytic pathway revealed that CD28 stimulation induced the increase of c-myc and the glucose transporter Glut1 in CD4+ T cells from RRMS. CD28-induced increase of glycolysis was also associated with the up-regulation of pro-inflammatory cytokines, most of which were related to the Th17 cell phenotype, as demonstrated by the strong inhibition exerted by the glycolysis inhibitor 2-deoxy-D-glucose. Finally, treatment of CD4+ T cells from RRMS patients with a class 1A PI3K inhibitor strongly impaired CD28-induced glycolysis, c-myc and Glut1 expressions, as well as the up-regulation of pro-inflammatory cytokines. Conclusion: Altogether these data strongly suggest a role of CD28 and associated class 1A PI3K in reprogramming the metabolic process that maintain/amplify the inflammatory phenotype of peripheral T cells in RRMS patients

Binding of Staphylococcal Enterotoxin B (SEB) to B7 Receptors Triggers TCR- and CD28-Mediated Inflammatory Signals in the Absence of MHC Class II Molecules

The inflammatory activity of staphylococcal enterotoxin B (SEB) relies on its capacity to trigger polyclonal T-cell activation by binding both T-cell receptor (TCR) and costimulatory receptor CD28 on T cells and MHC class II and B7 molecules on antigen presenting cells (APC). Previous studies highlighted that SEB may bind TCR and CD28 molecules independently of MHC class II, yet the relative contribution of these interactions to the pro-inflammatory function of SEB remained unclear. Here, we show that binding to MHC class II is dispensable for the inflammatory activity of SEB, whereas binding to TCR, CD28 and B7 molecules is pivotal, in both human primary T cells and Jurkat T cell lines. In particular, our finding is that binding of SEB to B7 molecules suffices to trigger both TCR- and CD28-mediated inflammatory signalling. We also provide evidence that, by strengthening the interaction between CD28 and B7, SEB favours the recruitment of the TCR into the immunological synapse, thus inducing lethal inflammatory signalling