Gaetano Naselli

Pro-Inflammatory CD11c+CD206+ Adipose Tissue Macrophages Are Associated With Insulin Resistance in Human Obesity

OBJECTIVE Insulin resistance and other features of the metabolic syndrome have been causally linked to adipose tissue macrophages (ATMs) in mice with diet-induced obesity. We aimed to characterize macrophage phenotype and function in human subcutaneous and omental adipose tissue in relation to insulin resistance in obesity. RESEARCH DESIGN AND METHODS Adipose tissue was obtained from lean and obese women undergoing bariatric surgery. Metabolic markers were measured in fasting serum and ATMs characterized by immunohistology, flow cytometry, and tissue culture studies. RESULTS ATMs comprised CD11c+CD206+ cells in “crown” aggregates and solitary CD11c−CD206+ cells at adipocyte junctions. In obese women, CD11c+ ATM density was greater in subcutaneous than omental adipose tissue and correlated with markers of insulin resistance. CD11c+ ATMs were distinguished by high expression of integrins and antigen presentation molecules; interleukin (IL)-1β, -6, -8, and -10; tumor necrosis factor-α; and CC chemokine ligand-3, indicative of an activated, proinflammatory state. In addition, CD11c+ ATMs were enriched for mitochondria and for RNA transcripts encoding mitochondrial, proteasomal, and lysosomal proteins, fatty acid metabolism enzymes, and T-cell chemoattractants, whereas CD11c− ATMs were enriched for transcripts involved in tissue maintenance and repair. Tissue culture medium conditioned by CD11c+ ATMs, but not CD11c− ATMs or other stromovascular cells, impaired insulin-stimulated glucose uptake by human adipocytes. CONCLUSIONS These findings identify proinflammatory CD11c+ ATMs as markers of insulin resistance in human obesity. In addition, the machinery of CD11c+ ATMs indicates they metabolize lipid and may initiate adaptive immune responses.

SPAK, a STE20/SPS1-related kinase that activates the p38 pathway

We have cloned a member of the STE20/SPS1 protein kinase family from a transformed rat pancreatic beta cell line. SPAK (STE20/SPS1-related, proline alanine-rich kinase) belongs to the SPS1 subfamily of STE20 kinases and is highly conserved between species. SPAK is expressed ubiquitously, although preferentially in brain and pancreas. Biochemical characterization of SPAK catalytic activity demonstrates that is a serine/threonine kinase that can phosphorylate itself and an exogenous substrate in vitro. SPAK is immunoprecipitated from transfected mammalian cells as a complex with another, as yet uncharacterized, serine/threonine kinase which is capable of phosphorylating catalytically-inactive SPAK and myelin basic protein in an in vitro kinase assay. SPAK specifically activates the p38 pathway in cotransfection assays. Like MST1 and MST2, SPAK contains a putative caspase cleavage site at the junction of the catalytic domain and the C-terminal region. Full-length SPAK is expressed in the cytoplasm in transfected cells, while a mutant corresponding to caspase-cleaved SPAK is expressed predominantly in the nucleus. The similarity of SPAK to other SPS1 family members, its ability to activate the p38 pathway, in addition to its putative caspase cleavage site, provide evidence that SPAK may act as a novel mediator of stress-activated signals.

Distinct Distribution of Laminin and Its Integrin Receptors In The Pancreas

Tissue function is regulated by the extracellular microenvironment including cell basement membranes, in which laminins are a major component. Previously, we found that laminin-1 promotes differentiation and survival of pancreatic islet cells. Here we characterize the expression pattern of laminins and their integrin receptors in adult pancreas. Although they are expressed in the basement membrane of acinar cells and duct epithelium, no laminin chains examined were detected extracellularly in the pancreatic islets. In contrast to laminin β1- and γ1-chains, the α1-chain, unique to laminin-1, was not detected. Laminin-10 (α5β1γ1) was expressed in acinar tissue, whereas laminins-2 (α2β1γ1) and -10 were expressed in the blood vessels. The laminin connector molecule, nidogen-1, had a distribution similar to that of laminin β1 and γ1, whereas fibulin-1 and -2, which compete with nidogen-1, were mostly confined to blood vessels. Integrin subunits α6 and α3 were detected in acinar cells and duct epithelial cells, but α6 was absent in islet cells. Integrin α6β4 was detected only in duct cells, α6β1 in both acinar and ductal cells, and α3β1 in acinar, duct, and islet cells. These findings are a basis for further investigation of the role of extracellular matrix molecules and their receptors in pancreas function.

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.

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.

The A-chain of insulin is a hot-spot for CD4 + T cell epitopes in human type 1 diabetes

Type 1 diabetes (T1D) is caused by T cell‐mediated destruction of the pancreatic insulin‐producing β cells. While the role of CD4+ T cells in the pathogenesis of T1D is accepted widely, the epitopes recognized by pathogenic human CD4+ T cells remain poorly defined. None the less, responses to the N‐terminal region of the insulin A‐chain have been described. Human CD4+ T cells from the pancreatic lymph nodes of subjects with T1D respond to the first 15 amino acids of the insulin A‐chain. We identified a human leucocyte antigen‐DR4‐restricted epitope comprising the first 13 amino acids of the insulin A‐chain (A1‐13), dependent upon generation of a vicinal disulphide bond between adjacent cysteines (A6–A7). Here we describe the analysis of a CD4+ T cell clone, isolated from a subject with T1D, which recognizes a new HLR‐DR4‐restricted epitope (KRGIVEQCCTSICS) that overlaps the insulin A1‐13 epitope. This is a novel epitope, because the clone responds to proinsulin but not to insulin, T cell recognition requires the last two residues of the C‐peptide (Lys, Arg) and recognition does not depend upon a vicinal disulphide bond between the A6 and A7 cysteines. The finding of a further CD4+ T cell epitope in the N‐terminal A‐chain region of human insulin underscores the importance of this region as a target of CD4+ T cell responses in human T1D.

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.

acDCs enhance human antigen–specific T-cell responses

Detection of human Ag-specific T cells is limited by sensitivity and blood requirements. As dendritic cells (DCs) can potently stimulate T cells, we hypothesized that their induction in PBMCs in situ could link Ag processing and presentation to Ag-specific T-cell activation. To this end, unfractionated PBMCs (fresh or frozen) or whole blood were incubated for 48 hours with protein or peptide Ag together with different DC-activating agents to rapidly and sequentially induce, pulse, and mature DCs. DC activation was therefore lined up with Ag recognition by neighboring T cells, thus telescoping the sequential steps of T-cell activation. Efficient processing of protein Ags made prior knowledge of epitopes and HLA restrictions dispensable. While reducing stimulation time, manipulation and blood requirements, in situ DC induction specifically amplified Ag-specific T-cell responses (cytokine secretion, proliferation, CD137/CD154 up-regulation, and binding of peptide-HLA multimers). IL-1β, although released by DCs, was also secreted in an Ag-specific fashion, thus providing an indirect biomarker of T-cell responses. These accelerated cocultured DC (acDC) assays offered a sensitive means with which to evaluate T-cell responses to viral and melanoma Ag vaccination, and may therefore find application for immune monitoring in viral, tumor, autoimmune, and transplantation settings.

SEROLOGICAL DIAGNOSIS OF PRIMARY SJÖGREN'S SYNDROME BY MEANS OF HUMAN RECOMBINANT La (SS-B) AS NUCLEAR ANTIGEN

Human recombinant La nucleoprotein was purified from cultures of Escherichia coli containing a vector with a 1.4 kilobase cDNA encoding La; the nucleoprotein was used to test for antinuclear antibodies (ANA) to La. Serum samples from 260 patients with autoimmune diseases associated with ANA and 100 healthy subjects were tested by an enzyme-linked immunosorbent assay (ELISA). Samples from 47 (94%) of 50 patients with primary Sjögrens syndrome and 1 (7%) of 14 patients with secondary Sjögrens syndrome reacted with the recombinant La. No reactivity was demonstrated in 196 patients with other ANA-associated autoimmune diseases or in 100 healthy subjects. The study confirms the high correlation between ANA, anti-La, and primary Sjögrens syndrome and shows how gene cloning can provide large quantities of human autoantigens for use in highly specific and sensitive diagnostic assays.

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.