Biomedical subjects

Pere Santamaria

Publications and source records attributed to Pere Santamaria.

At least 19 recordsLinked to original sources

PubMed2006

TRPV1+ sensory neurons control beta cell stress and islet inflammation in autoimmune diabetes.

In type 1 diabetes, T cell-mediated death of pancreatic beta cells produces insulin deficiency. However, what attracts or restricts broadly autoreactive lymphocyte pools to the pancreas remains unclear. We report that TRPV1(+) pancreatic sensory neurons control islet inflammation and insulin resistance. Eliminating these neurons in diabetes-prone NOD mice prevents insulitis and diabetes, despite systemic persistence of pathogenic T cell pools. Insulin resistance and beta cell stress of prediabetic NOD mice are prevented when TRPV1(+) neurons are eliminated. TRPV1(NOD), localized to the Idd4.1 diabetes-risk locus, is a hypofunctional mutant, mediating depressed neurogenic inflammation. Delivering the neuropeptide substance P by intra-arterial injection into the NOD pancreas reverses abnormal insulin resistance, insulitis, and diabetes for weeks. Concordantly, insulin sensitivity is enhanced in trpv1(-/-) mice, whereas insulitis/diabetes-resistant NODxB6Idd4-congenic mice, carrying wild-type TRPV1, show restored TRPV1 function and insulin sensitivity. Our data uncover a fundamental role for insulin-responsive TRPV1(+) sensory neurons in beta cell function and diabetes pathoetiology.

Animals↗

PubMed2006

IL-1 beta breaks tolerance through expansion of CD25+ effector T cells.

IL-1 is a key proinflammatory driver of several autoimmune diseases including juvenile inflammatory arthritis, diseases with mutations in the NALP/cryopyrin complex and Crohn's disease, and is genetically or clinically associated with many others. IL-1 is a pleiotropic proinflammatory cytokine; however the mechanisms by which increased IL-1 signaling promotes autoreactive T cell activity are not clear. Here we show that autoimmune-prone NOD and IL-1 receptor antagonist-deficient C57BL/6 mice both produce high levels of IL-1, which drives autoreactive effector cell expansion. IL-1beta drives proliferation and cytokine production by CD4(+)CD25(+)FoxP3(-) effector/memory T cells, attenuates CD4(+)CD25(+)FoxP3(+) regulatory T cell function, and allows escape of CD4(+)CD25(-) autoreactive effectors from suppression. Thus, inflammation or constitutive overexpression of IL-1beta in a genetically predisposed host can promote autoreactive effector T cell expansion and function, which attenuates the ability of regulatory T cells to maintain tolerance to self.

Animals↗

PubMed2006

The combined effects of tryptophan starvation and tryptophan catabolites down-regulate T cell receptor zeta-chain and induce a regulatory phenotype in naive T cells.

Tryptophan catabolism is a tolerogenic effector system in regulatory T cell function, yet the general mechanisms whereby tryptophan catabolism affects T cell responses remain unclear. We provide evidence that the short-term, combined effects of tryptophan deprivation and tryptophan catabolites result in GCN2 kinase-dependent down-regulation of the TCR zeta-chain in murine CD8+ T cells. TCR zeta down-regulation can be demonstrated in vivo and is associated with an impaired cytotoxic effector function in vitro. The longer-term effects of tryptophan catabolism include the emergence of a regulatory phenotype in naive CD4+CD25- T cells via TGF-beta induction of the forkhead transcription factor Foxp3. Such converted cells appear to be CD25+, CD69-, CD45RBlow, CD62L+, CTLA-4+, BTLAlow and GITR+, and are capable of effective control of diabetogenic T cells when transferred in vivo. Thus, both tryptophan starvation and tryptophan catabolites contribute to establishing a regulatory environment affecting CD8+ as well as CD4+ T cell function, and not only is tryptophan catabolism an effector mechanism of tolerance, but it also results in GCN2-dependent generation of autoimmune-preventive regulatory T cells.

Animals↗

PubMed2006

Modeling competition among autoreactive CD8+ T cells in autoimmune diabetes: implications for antigen-specific therapy.

Antigen therapy remains a promising strategy for prevention and treatment of autoimmune diseases, but translating this strategy to clinical therapy has been largely unsuccessful. We have shown that development of autoimmune diabetes in non-obese diabetic (NOD) mice involves prevalent recruitment of CD8+ T cells recognizing epitopes of islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP). Administration of peptide analogs of IGRP206-214, the dominant epitope, reduced disease incidence but only under conditions that led to selective deletion of high-avidity T-cell clones. Peptide types or doses that resulted in elimination of all IGRP206-214-reactive T cells, regardless of avidity, promoted the recruitment of sub-dominant epitope-specific T cells and failed to prevent disease development. Here, we mathematically model competition of IGRP-reactive T-cell clones during spontaneous disease, and in response to peptide treatment. Based on realistic T-cell activation, proliferation and differentiation parameter values, our model shows that progression of spontaneous disease is characterized by (i) initial expansion of all IGRP206-214-reactive T-cell clones (irrespective of avidity) and (ii) slow replacement of T-cell clones recognizing peptide/MHC with low avidity by their high-avidity counterparts. This model helps understand the paradoxical outcomes of IGRP-based peptide treatment experiments. Furthermore, it predicts that slight deviations in dose or peptide affinity can lead to treatment failure or disease progression. This will occur if the treatment (i) increases the imbalance between competing IGRP206-214-reactive T-cell clones such that it favors rapid takeover of high-avidity clones or (ii) deletes all IGRP206-214-reactive clones, thereby creating a vacuum that promotes the recruitment of pathogenic sub-dominant specificities. Our data and model urge caution in the application of peptide therapy in autoimmunity.

Animals↗

PubMed2006

Lessons on autoimmune diabetes from animal models.

T1DM (Type I diabetes mellitus) results from selective destruction of the insulin-producing beta-cells of the pancreas by the immune system, and is characterized by hyperglycaemia and vascular complications arising from suboptimal control of blood glucose levels. The discovery of animal models of T1DM in the late 1970s and early 1980s, particularly the NOD (non-obese diabetic) mouse and the BB (BioBreeding) diabetes-prone rat, had a fundamental impact on our ability to understand the genetics, aetiology and pathogenesis of this disease. NOD and BB diabetes-prone rats spontaneously develop a form of diabetes that closely resembles the human counterpart. Early studies of these animals quickly led to the realization that T1DM is caused by autoreactive T-lymphocytes and revealed that the development of T1DM is controlled by numerous polymorphic genetic elements that are scattered throughout the genome. The development of transgenic and gene-targeting technologies during the 1980s allowed the generation of models of T1DM of reduced genetic and pathogenic complexity, and a more detailed understanding of the immunogenetics of T1DM. In this review, we summarize the contribution of studies in animal models of T1DM to our current understanding of four fundamental aspects of T1DM: (i) the nature of genetic elements affording T1DM susceptibility or resistance; (ii) the mechanisms underlying the development and recruitment of pathogenic autoreactive T-cells; (iii) the identity of islet antigens that contribute to the initiation and/or progression of islet inflammation and beta-cell destruction; and (iv) the design of avenues for therapeutic intervention that are rooted in the knowledge gained from studies of animal models. Development of new animal models will ensure continued progress in these four areas.

Animals↗

PubMed2006

Cytotoxic T-cells from T-cell receptor transgenic NOD8.3 mice destroy beta-cells via the perforin and Fas pathways.

Cytotoxic T-cells are the major mediators of beta-cell destruction in type 1 diabetes, but the molecular mechanisms are not definitively established. We have examined the contribution of perforin and Fas ligand to beta-cell destruction using islet-specific CD8(+) T-cells from T-cell receptor transgenic NOD8.3 mice. NOD8.3 T-cells killed Fas-deficient islets in vitro and in vivo. Perforin-deficient NOD8.3 T-cells were able to destroy wild-type but not Fas-deficient islets in vitro. These results imply that NOD8.3 T-cells use both pathways and that Fas is required for beta-cell killing only when perforin is missing. Consistent with this theory, transgenic NOD8.3 mice with beta-cells that do not respond to Fas ligation were not protected from diabetes. We next investigated the mechanism of protection provided by overexpression of suppressor of cytokine signaling-1 (SOCS-1) in beta-cells of NOD8.3 mice. SOCS-1 islets remained intact when grafted into NOD8.3 mice and were less efficiently killed in vitro. However, addition of exogenous peptide rendered SOCS-1 islets susceptible to 8.3 T-cell-mediated lysis. Therefore, NOD8.3 T-cells use both perforin and Fas pathways to kill beta-cells and the surprising blockade of NOD8.3 T-cell-mediated beta-cell death by SOCS-1 overexpression may be due in part to reduced target cell recognition.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Visualizing regulatory T cell control of autoimmune responses in nonobese diabetic mice.

The in vivo mechanism of regulatory T cell (T(reg) cell) function in controlling autoimmunity remains controversial. Here we have used two-photon laser-scanning microscopy to analyze lymph node priming of diabetogenic T cells and to delineate the mechanisms of T(reg) cell control of autoimmunity in vivo. Islet antigen-specific CD4(+)CD25(-) T helper cells (T(H) cells) and T(reg) cells swarmed and arrested in the presence of autoantigens. These T(H) cell activities were progressively inhibited in the presence of increasing numbers of T(reg) cells. There were no detectable stable associations between T(reg) and T(H) cells during active suppression. In contrast, T(reg) cells directly interacted with dendritic cells bearing islet antigen. Such persistent T(reg) cell-dendritic cell contacts preceded the inhibition of T(H) cell activation by dendritic cells, supporting the idea that dendritic cells are central to T(reg) cell function in vivo.

Adoptive Transfer↗

PubMed2005

To 'B' regulated: B cells as members of the regulatory workforce.

Until recently, immune regulation was thought to be predominantly mediated by specialized subsets of T lymphocytes. However, although B lymphocytes have previously been shown to have regulatory properties in autoimmunity, a recent report by Knoechel et al. establishes a role for B lymphocytes in the control of pathogenic autoreactive T cell responses arising when the number of lymphocytes is abnormally low (lymphopenia).

Animals↗

PubMed2005

CD8+ T cells in autoimmunity.

Mounting evidence shows that CD8(+) T cells contribute to the initiation, progression and regulation of several pathogenic autoimmune responses in which these cells were not previously thought to play a major role. CD8(+) T cells can kill target cells directly, by recognizing peptide-MHC complexes on target cells, or indirectly, by secreting cytokines capable of signaling through death receptors expressed on the target cell surface. Autoreactive CD8(+) T cells can also contribute to autoimmunity by releasing cytokines capable of increasing the susceptibility of target cells to cytotoxicity, or by secreting chemokines that attract other immune cells to the site of autoimmunity. Autoreactive CD8(+) T cells can also downregulate autoimmune responses. Recent important advances include a mechanistic understanding of events leading to the activation and recruitment of autoreactive CD8(+) T cells in certain autoimmune responses and a greater appreciation of the diverse roles that these T cells play in autoimmunity.

Animals↗

PubMed2005

Developmental control of CD8 T cell-avidity maturation in autoimmune diabetes.

The progression of immune responses is generally associated with an increase in the overall avidity of antigen-specific T cell populations for peptide-MHC. This is thought to result from preferential expansion of high-avidity clonotypes at the expense of their low-avidity counterparts. Since T cell antigen-receptor genes do not mutate, it is puzzling that high-avidity clonotypes do not predominate from the outset. Here we provide a developmental basis for this phenomenon in the context of autoimmunity. We have carried out comprehensive studies of the diabetogenic CD8 T cell population that targets residues 206-214 of the beta cell antigen islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP(206-214)) and undergoes avidity maturation as disease progresses. We find that the succession of IGRP(206-214)-specific clonotypes with increasing avidities during the progression of islet inflammation to overt diabetes in nonobese diabetic mice is fueled by autoimmune inflammation but opposed by systemic tolerance. As expected, naive high-avidity IGRP(206-214)-specific T cells respond more efficiently to antigen and are significantly more diabetogenic than their intermediate- or low-avidity counterparts. However, central and peripheral tolerance selectively limit the contribution of these high-avidity T cells to the earliest stages of disease without abrogating their ability to progressively accumulate in inflamed islets and kill beta cells. These results illustrate the way in which incomplete deletion of autoreactive T cell populations of relatively high avidity can contribute to the development of pathogenic autoimmunity in the periphery.

Animals↗

PubMed2005

Prevention of diabetes by manipulation of anti-IGRP autoimmunity: high efficiency of a low-affinity peptide.

Antigen therapy may hold great promise for the prevention of autoimmunity; however, most clinical trials have failed, suggesting that the principles guiding the choice of treatment remain ill defined. Here, we examine the antidiabetogenic properties of altered peptide ligands of CD8+ T cells recognizing an epitope of islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP206-214), a prevalent population of autoreactive T cells in autoimmune diabetes. We show that islet-associated CD8+ T cells in nonobese diabetic mice recognize numerous IGRP epitopes, and that these cells have a role in the outcome of protocols designed to induce IGRP206-214-specific tolerance. Ligands targeting IGRP206-214-reactive T cells prevented disease, but only at doses that spared low-avidity clonotypes. Notably, near complete depletion of the IGRP206-214-reactive T-cell pool enhanced the recruitment of subdominant specificities and did not blunt diabetogenesis. Thus, peptide therapy in autoimmunity is most effective under conditions that foster occupation of the target organ lymphocyte niche by nonpathogenic, low-avidity clonotypes.

Animals↗

PubMed2005

Rules of recruitment for Th1 and Th2 lymphocytes in inflamed liver: a role for alpha-4 integrin and vascular adhesion protein-1.

The mechanisms that mediate the recruitment of Th1 and Th2 lymphocytes in vivo are poorly understood. We demonstrate that the mechanisms by which exogenously produced CD4(+) Th1 and Th2 cells roll and adhere in Con A-inflamed liver microcirculation differ dramatically: Th1 cells use alpha(4)beta(1)-integrin and Th2 cells use the vascular adhesion protein (VAP)-1. P-selectin plays no detectable role in Th1 or Th2 cell trafficking in liver microcirculation. Cellular recruitment in the liver sinusoids has previously been shown to be independent of many known adhesion molecules, leading to the suggestion that recruitment in these structures is mediated by physical trapping. While this may still be true for neutrophils, Th1 and Th2 cells use alpha(4)-integrin and VAP-1, respectively, to adhere within the liver sinusoids.

Amine Oxidase (Copper-Containing)↗

PubMed2005

Islet-infiltrating B-cells in nonobese diabetic mice predominantly target nervous system elements.

B-cells accumulate in pancreatic islets during the autoimmune response that precedes the onset of type 1 diabetes. However, the role and antigenic specificity of these cells remain a mystery. To elucidate the antigenic repertoire of islet-infiltrating B-cells in type 1 diabetes, we generated hybridoma cell lines of islet-infiltrating B-cells from nonobese diabetic (NOD) mice and NOD mice expressing a diabetogenic T-cell receptor (8.3-NOD). Surprisingly, characterization of the tissue specificity of the antibodies secreted by these cells revealed that a predominant fraction of these hybridomas produce antibodies specific for the pancreatic nervous system. Similar results were obtained with B-cell hybridomas derived from mild insulinic lesions of diabetes-resistant (NOD x NOR)F1 and 8.3-(NOD x NOR)F1 mice. Immunoglobulin class analyses further indicated that most islet-derived hybridomas had arisen from B-cells that had undergone immunoglobulin class switch recombination, suggesting that islet-associated B-cells are involved in active, T-helper-driven immune responses against local antigenic targets. This is the first evidence showing the existence of a predominant active B-cell response in situ against pancreatic nervous system elements in diabetogenesis. Our data are consistent with the idea that this B-cell response precedes the progression of insulitis to overt diabetes, thus strongly supporting the idea that pancreatic nervous system elements are early targets in type 1 diabetes.

Animals↗

PubMed2004

Individual nonobese diabetic mice exhibit unique patterns of CD8+ T cell reactivity to three islet antigens, including the newly identified widely expressed dystrophia myotonica kinase.

Spontaneous autoimmune diabetes development in NOD mice requires both CD8(+) and CD4(+) T cells. Three pathogenic CD8(+) T cell populations (represented by the G9C8, 8.3, and AI4 clones) have been described. Although the Ags for G9C8 and 8.3 are known to be insulin and islet-specific glucose-6-phosphatase catalytic subunit-related protein, respectively, only mimotope peptides had previously been identified for AI4. In this study, we used peptide/MHC tetramers to detect and quantify these three pathogenic populations among beta cell-reactive T cells cultured from islets of individual NOD mice. Even within age-matched groups, each individual mouse exhibited a unique distribution of beta cell-reactive CD8(+) T cells, both in terms of the number of tetramer-staining populations and the relative proportion of each population in the islet infiltrate. Thus, the inflammatory process in each individual follows its own distinctive course. Screening of a combinatorial peptide library in positional scanning format led to the identification of a peptide derived from dystrophia myotonica kinase (DMK) that is recognized by AI4-like T cells. Importantly, the antigenic peptide is naturally processed and presented by DMK-transfected cells. DMK is a widely expressed protein that is nonetheless the target of a beta cell-specific autoimmune response.

Animals↗

PubMed2004

Progression of spontaneous autoimmune diabetes is associated with a switch in the killing mechanism used by autoreactive CTL.

Autoimmune (type 1) diabetes mellitus results from the destruction of insulin-producing pancreatic beta-cells by T lymphocytes. Beta-cell death that is induced by autoreactive CTL in diabetes involves both Fas/Fas ligand (FasL)- and perforin/granzyme-mediated pathways, although their relative contributions during the progression of the disease remain unknown. We demonstrate here that despite the preferential use of the Fas/FasL pathway for cytolysis of beta-cell targets, transgenic beta-cell-specific CTL were able to kill targets via the perforin pathway when triggered by a higher affinity stimulus. In addition, we show that the killing mechanism used by islet-associated CD8(+) T cells from non-obese diabetic mice changed as the mice aged and correspondingly, with the stage of diabetes. These results provide direct evidence for age-related changes in the cytotoxic pathways used by diabetogenic T cells during the progression of autoimmune diabetes.

Aging↗

PubMed2004

Perturbed homeostasis of peripheral T cells elicits decreased susceptibility to anti-CD3-induced apoptosis in prediabetic nonobese diabetic mice.

Activation-induced cell death (AICD) plays a key role in the homeostasis of the immune system. Autoreactive T cells are eliminated through AICD both from the thymus and periphery. In this study, we show that NOD peripheral T cells, especially CD8(+) T cells, display a decreased susceptibility to anti-CD3-induced AICD in vivo compared with T cells from diabetes-resistant B6, nonobese diabetes-resistant, and NOD.B6Idd4 mice. The susceptibility of NOD CD8(+) T cells to AICD varies in an age- and dose-dependent manner upon stimulation in vivo with either a mitogenic or nonmitogenic anti-CD3. NOD T cells preactivated by anti-CD3 in vivo are less susceptible than B6 T cells to TCR-induced AICD. Treatment of NOD mice with a mitogenic anti-CD3 depletes CD4(+)CD25(-)CD62L(+) but not CD4(+)CD25(+)CD62L(+) T cells, thereby resulting in an increase of the latter subset in the spleen. Treatment with a nonmitogenic anti-CD3 mAb delays the onset of T1D in 8.3 TCR transgenic NOD mice. These results demonstrate that the capacity of anti-CD3 to protect NOD mice from T1D correlates with its ability to perturb T cell homeostasis by inducing CD8(+) T cell AICD and increasing the number of CD4(+)CD25(+)CD62L(+) T cells in the periphery.

Aging↗

PubMed2004

Requirement for both H-2Db and H-2Kd for the induction of diabetes by the promiscuous CD8+ T cell clonotype AI4.

The NOD mouse is a model for autoimmune type 1 diabetes in humans. CD8(+) T cells are essential for the destruction of the insulin-producing pancreatic beta cells characterizing this disease. AI4 is a pathogenic CD8(+) T cell clone, isolated from the islets of a 5-wk-old female NOD mouse, which is capable of mediating overt diabetes in the absence of CD4(+) T cell help. Recent studies using MHC-congenic NOD mice revealed marked promiscuity of the AI4 TCR, as the selection of this clonotype can be influenced by multiple MHC molecules, including some class II variants. The present work was designed, in part, to determine whether similar promiscuity also characterizes the effector function of mature AI4 CTL. Using splenocyte and bone marrow disease transfer models and in vitro islet-killing assays, we report that efficient recognition and destruction of beta cells by AI4 requires the beta cells to simultaneously express both H-2D(b) and H-2K(d) class I MHC molecules. The ability of the AI4 TCR to interact with both H-2D(b) and H-2K(d) was confirmed using recombinant peptide libraries. This approach also allowed us to define a mimotope peptide recognized by AI4 in an H-2D(b)-restricted manner. Using ELISPOT and mimotope/H-2D(b) tetramer analyses, we demonstrate for the first time that AI4 represents a readily detectable T cell population in the islet infiltrates of prediabetic NOD mice. Our identification of a ligand for AI4-like T cells will facilitate further characterization and manipulation of this pathogenic and promiscuous T cell population.

Adoptive Transfer↗

PubMed2004

Suppressor of cytokine signaling-1 overexpression protects pancreatic beta cells from CD8+ T cell-mediated autoimmune destruction.

In type 1 diabetes, cytokine action on beta cells potentially contributes to beta cell destruction by direct cytotoxicity, inducing Fas expression, and up-regulating class I MHC and chemokine expression to increase immune recognition. To simultaneously block beta cell responsiveness to multiple cytokines, we overexpressed suppressor of cytokine signaling-1 (SOCS-1). This completely prevented progression to diabetes in CD8(+) TCR transgenic nonobese diabetic (NOD) 8.3 mice without affecting pancreas infiltration and partially prevented diabetes in nontransgenic NOD mice. SOCS-1 appeared to protect at least in part by inhibiting TNF- and IFN-gamma-induced Fas expression on beta cells. Fas expression was up-regulated on beta cells in vivo in prediabetic NOD8.3 mice, and this was inhibited by SOCS-1. Additionally, IFN-gamma-induced class I MHC up-regulation and TNF- and IFN-gamma-induced IL-15 expression by beta cells were inhibited by SOCS-1, which correlated with suppressed 8.3 T cell proliferation in vitro. Despite this, 8.3 T cell priming in vivo appeared unaffected. Therefore, blocking beta cell responses to cytokines impairs recognition by CD8(+) T cells and blocks multiple mechanisms of beta cell destruction, but does not prevent T cell priming and recruitment to the islets. Our findings suggest that increasing SOCS-1 expression may be useful as a strategy to block CD8(+) T cell-mediated type 1 diabetes as well as to more generally prevent cytokine-dependent tissue destruction in inflammatory diseases.

Adoptive Transfer↗