Yuxia Zhang

Genome-wide DNA methylation analysis identifies hypomethylated genes regulated by FOXP3 in human regulatory T cells

Regulatory T cells (Treg) prevent the emergence of autoimmune disease. Prototypic natural Treg (nTreg) can be reliably identified by demethylation at the Forkhead-box P3 (FOXP3) locus. To explore the methylation landscape of nTreg, we analyzed genome-wide methylation in human naive nTreg (rTreg) and conventional naive CD4(+) T cells (Naive). We detected 2315 differentially methylated cytosine-guanosine dinucleotides (CpGs) between these 2 cell types, many of which clustered into 127 regions of differential methylation (RDMs). Activation changed the methylation status of 466 CpGs and 18 RDMs in Naive but did not alter DNA methylation in rTreg. Gene-set testing of the 127 RDMs showed that promoter methylation and gene expression were reciprocally related. RDMs were enriched for putative FOXP3-binding motifs. Moreover, CpGs within known FOXP3-binding regions in the genome were hypomethylated. In support of the view that methylation limits access of FOXP3 to its DNA targets, we showed that increased expression of the immune suppressive receptor T-cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain (TIGIT), which delineated Treg from activated effector T cells, was associated with hypomethylation and FOXP3 binding at the TIGIT locus. Differential methylation analysis provides insight into previously undefined human Treg signature genes and their mode of regulation.

T cell regulation mediated by interaction of soluble CD52 with the inhibitory receptor Siglec-10

Functionally diverse T cell populations interact to maintain homeostasis of the immune system. We found that human and mouse antigen-activated T cells with high expression of the lymphocyte surface marker CD52 suppressed other T cells. CD52hiCD4+ T cells were distinct from CD4+CD25+Foxp3+ regulatory T cells. Their suppression was mediated by soluble CD52 released by phospholipase C. Soluble CD52 bound to the inhibitory receptor Siglec-10 and impaired phosphorylation of the T cell receptor–associated kinases Lck and Zap70 and T cell activation. Humans with type 1 diabetes had a lower frequency and diminished function of CD52hiCD4+ T cells responsive to the autoantigen GAD65. In diabetes-prone mice of the nonobese diabetic (NOD) strain, transfer of lymphocyte populations depleted of CD52hi cells resulted in a substantially accelerated onset of diabetes. Our studies identify a ligand-receptor mechanism of T cell regulation that may protect humans and mice from autoimmune disease.

The polycomb repressive complex 2 governs life and death of peripheral T cells

Differentiation of naïve CD4(+) T cells into effector (Th1, Th2, and Th17) and induced regulatory (iTreg) T cells requires lineage-specifying transcription factors and epigenetic modifications that allow appropriate repression or activation of gene transcription. The epigenetic silencing of cytokine genes is associated with the repressive H3K27 trimethylation mark, mediated by the Ezh2 or Ezh1 methyltransferase components of the polycomb repressive complex 2 (PRC2). Here we show that silencing of the Ifng, Gata3, and Il10 loci in naïve CD4(+) T cells is dependent on Ezh2. Naïve CD4(+) T cells lacking Ezh2 were epigenetically primed for overproduction of IFN-γ in Th2 and iTreg and IL-10 in Th2 cells. In addition, deficiency of Ezh2 accelerated effector Th cell death via death receptor-mediated extrinsic and intrinsic apoptotic pathways, confirmed in vivo for Ezh2-null IFN-γ-producing CD4(+) and CD8(+) T cells responding to Listeria monocytogenes infection. These findings demonstrate the key role of PRC2/Ezh2 in differentiation and survival of peripheral T cells and reveal potential immunotherapeutic targets.

Cord blood monocyte-derived inflammatory cytokines suppress IL-2 and induce nonclassic "T(H)2-type" immunity associated with development of food allergy

Infants who develop food allergy display hyperresponsive innate immunity at birth that promotes nonclassical TH2 differentiation. Fighting food allergy For people with food allergies, a slice of pizza or a peanut butter sandwich can be deadly. Yet despite the increasing prevalence of food allergy, little is known as to the immunological causes. Now, Zhang et al. report that infants who later developed food allergy had altered immunity at birth. Cord blood from these infants had more monocytes compared with CD4+ T cells and decreased numbers of regulatory T cells. Moreover, the monocytes from food-allergic infants secreted more inflammatory cytokines than those from healthy infants. These cytokines suppressed interleukin-2 (IL-2) expression by CD4+ T cells and skewed differentiation of these cells to a nonclassical T helper 2 (TH2) phenotype. Anti-inflammatory strategies should therefore be considered in preventing food allergy in these individuals. Food allergy is a major health burden in early childhood. Infants who develop food allergy display a proinflammatory immune profile in cord blood, but how this is related to interleukin-4 (IL-4)/T helper 2 (TH2)–type immunity characteristic of allergy is unknown. In a general population-derived birth cohort, we found that in infants who developed food allergy, cord blood displayed a higher monocyte to CD4+ T cell ratio and a lower proportion of natural regulatory T cell (nTreg) in relation to duration of labor. CD14+ monocytes of food-allergic infants secreted higher amounts of inflammatory cytokines (IL-1β, IL-6, and tumor necrosis factor–α) in response to lipopolysaccharide. In the presence of the mucosal cytokine transforming growth factor–β, these inflammatory cytokines suppressed IL-2 expression by CD4+ T cells. In the absence of IL-2, inflammatory cytokines decreased the number of activated nTreg and diverted the differentiation of both nTreg and naïve CD4+ T cells toward an IL-4–expressing nonclassical TH2 phenotype. These findings provide a mechanistic explanation for susceptibility to food allergy in infants and suggest anti-inflammatory approaches to its prevention.

Immune Modulation by Vitamin D and Its Relevance to Food Allergy.

Apart from its classical function in bone and calcium metabolism, vitamin D is also involved in immune regulation and has been linked to various cancers, immune disorders and allergic diseases. Within the innate and adaptive immune systems, the vitamin D receptor and enzymes in monocytes, dendritic cells, epithelial cells, T lymphocytes and B lymphocytes mediate the immune modulatory actions of vitamin D. Vitamin D insufficiency/deficiency early in life has been identified as one of the risk factors for food allergy. Several studies have observed an association between increasing latitude and food allergy prevalence, plausibly linked to lower ultraviolet radiation (UVR) exposure and vitamin D synthesis in the skin. Along with mounting epidemiological evidence of a link between vitamin D status and food allergy, mice and human studies have shed light on the modulatory properties of vitamin D on the innate and adaptive immune systems. This review will summarize the literature on the metabolism and immune modulatory properties of vitamin D, with particular reference to food allergy.

Revisiting regulatory T cells in type 1 diabetes.

Purpose of review Regulatory T cells (Treg) maintain immune homeostasis and prevent autoimmune disease. This review summarizes the recent advances in Treg knowledge relevant to type 1 diabetes, focusing on Treg signature, antigen specificity and development and function in the face of inflammation. Recent findings Thymus-derived natural regulatory T cells (nTreg) programmed by the transcription factor forkhead box P3 (FOXP3) and peripheral-induced regulatory T cells (iTreg) have largely nonoverlapping T-cell receptor repertoires to self-antigens and jointly contribute to immune homeostasis. Initial reports that CD4+CD25+ (FOXP3+) Treg were impaired in frequency or function in type 1 diabetes have not been confirmed. The Treg-specific demethylated region in the FOXP3 locus in nTreg is, in contrast, methylated in iTreg and conventional T cells (Tconv) and is the only feature that reliably distinguishes activated human nTreg and Tconv. Inflammatory cytokines regulate extrathymic differentiation of nTreg but can also reprogram nTreg into Th17 or Th1 effectors and prevent the differentiation of iTreg. Summary The methylation status of the FOXP3 locus provides a means to re-examine Treg in autoimmune disease. nTreg and iTreg recognize different self-antigens. Shaping of Treg by the cytokine milieu has implications for the application of Treg cell-based immune therapies.

Antigen-based vaccination and prevention of type 1 diabetes

Insulin-dependent or type 1 diabetes (T1D) is a paradigm for prevention of autoimmune disease: Pancreatic β-cell autoantigens are defined, at-risk individuals can be identified before the onset of symptoms, and autoimmune diabetes is preventable in rodent models. Intervention in asymptomatic individuals before or after the onset of subclinical islet autoimmunity places a premium on safety, a requirement met only by lifestyle–dietary approaches or autoantigen-based vaccination to induce protective immune tolerance. Insulin is the key driver of autoimmune β-cell destruction in the nonobese diabetic (NOD) mouse model of T1D and is an early autoimmune target in children at risk for T1D. In the NOD mouse, mucosal administration of insulin induces regulatory T cells that protect against diabetes. The promise of autoantigen-specific vaccination in humans has yet to be realized, but recent trials of oral and nasal insulin vaccination in at-risk humans provide grounds for cautious optimism.

The Closely Related CD103+ Dendritic Cells (DCs) and Lymphoid-Resident CD8+ DCs Differ in Their Inflammatory Functions

Migratory CD103+ and lymphoid-resident CD8+ dendritic cells (DCs) share many attributes, such as dependence on the same transcription factors, cross-presenting ability and expression of certain surface molecules, such that it has been proposed they belong to a common sub-lineage. The functional diversity of the two DC types is nevertheless incompletely understood. Here we reveal that upon skin infection with herpes simplex virus, migratory CD103+ DCs from draining lymph nodes were more potent at inducing Th17 cytokine production by CD4+ T cells than CD8+ DCs. This superior capacity to drive Th17 responses was also evident in CD103+ DCs from uninfected mice. Their differential potency to induce Th17 differentiation was reflected by higher production of IL-1β and IL-6 by CD103+ DCs compared with CD8+ DCs upon stimulation. The two types of DCs from isolated lymph nodes also differ in expression of certain pattern recognition receptors. Furthermore, elevated levels of GM-CSF, typical of those found in inflammation, substantially increased the pool size of CD103+ DCs in lymph nodes and skin. We argue that varied levels of GM-CSF may explain the contrasting reports regarding the positive role of GM-CSF in regulating development of CD103+ DCs. Together, we find that these two developmentally closely-related DC subsets display functional differences and that GM-CSF has differential effect on the two types of DCs.

CD52 inhibits Toll-like receptor activation of NF-κB and triggers apoptosis to suppress inflammation.

Soluble CD52 is a small glycoprotein that suppresses T-cell activation, but its effect on innate immune cell function is unknown. Here we demonstrate that soluble CD52 inhibits Toll-like receptor and tumor necrosis factor receptor signaling to limit activation of NF-κB and thereby suppress the production of inflammatory cytokines by macrophages, monocytes and dendritic cells. At higher concentrations, soluble CD52 depletes the short-lived pro-survival protein MCL-1, contributing to activation of the BH3-only proteins BAX and BAK to cause intrinsic apoptotic cell death. In vivo, administration of soluble CD52 suppresses lipopolysaccharide (LPS)-induced cytokine secretion and other features of endotoxic shock, whereas genetic deletion of CD52 exacerbates LPS responses. Thus, soluble CD52 exhibits broad immune suppressive effects that signify its potential as an immunotherapeutic agent.

Corrigendum to 'MicroRNAs in CD4(+) T cell subsets are markers of disease risk and T cell dysfunction in individuals at risk for type 1 diabetes' [J. Autoimmun. 68C (2016) 52-61].

Corrigendum Corrigendum to ‘MicroRNAs in CD4þ T cell subsets are markers of disease risk and T cell dysfunction in individuals at risk for type 1 diabetes’ [J. Autoimmun. 68C (2016) 52e61] Yuxia Zhang a, b, , Zhi-Ping Feng a, , Gaetano Naselli , Fiona Bell , James Wettenhall a, , Priscilla Auyeung , Justine A. Ellis d, , Anne-Louise Ponsonby d, , Terence P. Speed a, , Mark M.W. Chong a, b, , Leonard C. Harrison a, b, * a The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia b Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, Australia c Division of Immunology, Guangzhou Institute of Pediatrics, Guangzhou Women and Childrens Medical Center, Guangzhou Medical University, 9 Jingsui Road, Tianhe, Guangzhou, Guangdong 510623, China d Murdoch Childrens Research Institute, Royal Childrens Hospital, 50 Flemington Rd, Parkville, Victoria 3052, Australia e Department of Paediatrics, University of Melbourne, Victoria 3010, Australia