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Pere Santamaria

Publications and source records attributed to Pere Santamaria.

At least 37 records · Page 2Linked to original sources
PubMed2004

A critical temporal window for selectin-dependent CD4+ lymphocyte homing and initiation of late-phase inflammation in contact sensitivity.

Contact sensitivity (CS) is an inflammatory disorder characterized by early and late phases of leukocyte recruitment. We used a noninvasive intravital microscopy technique allowing for the direct visualization of leukocyte rolling and adhesion on blood vessel endothelium. By blocking specific adhesion molecules, we elucidated the molecular mechanisms mediating early leukocyte recruitment to be E- and P-selectin and demonstrated that leukocyte recruitment in the late phase had a different adhesive profile (mainly alpha(4)-integrin). Complete blockade of E- and P-selectin within the first 2 h of leukocyte-endothelial cell interactions (but not later) eliminated selectin-independent leukocyte recruitment at 24 h. Despite the predominance of neutrophils in the early phase, specific elimination of CD4(+) lymphocytes in the early phase eliminated the late response. CD4(+) lymphocytes homed to skin via E- and P-selectin within the early phase and induced the late phase response. Addition of these same CD4(+) lymphocytes 2 h after antigen challenge was too late for these cells to home to the skin and induce late phase responses. Our data clearly demonstrate that the antigen-challenged microenvironment is only accessible to CD4(+) lymphocytes for the first 2 h, and that this process is essential for the subsequent recruitment of other leukocyte populations in late phase responses.

Adoptive Transfer↗
PubMed2004

Increased islet antigen presentation leads to type-1 diabetes in mice with autoimmune susceptibility.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is frequently used in preclinical and clinical protocols to modulate autoimmune responses, bone marrow transplants, and recovery from immune ablative therapies. The immunological outcome of such therapies is not fully understood. We tested the hypothesis that GM-CSF would enhance the maturation of antigen-presenting cells, facilitating presentation of beta-cell autoantigens to autoreactive T cells. We found that islet expression of GM-CSF greatly enhanced disease in male mice. Islet-derived APC but not splenic APC showed markedly enhanced capacity to stimulate in vitro proliferative responses of islet-antigen-specific autoreactive T cells. In vivo transfer of CD8(+) and CD4(+) T cells demonstrate that autoreactive T cells undergo extensive division in pancreatic lymph nodes of GM-CSF-transgenic mice compared with wild-type NOD male mice. Together, the results presented here demonstrate that expression of GM-CSF in the pancreas can enhance autoimmunity in disease-susceptible mice.

Adoptive Transfer↗
PubMed2004

NKG2D blockade prevents autoimmune diabetes in NOD mice.

NKG2D is an activating receptor on CD8(+) T cells and NK cells that has been implicated in immunity against tumors and microbial pathogens. Here we show that RAE-1 is present in prediabetic pancreas islets of NOD mice and that autoreactive CD8(+) T cells infiltrating the pancreas express NKG2D. Treatment with a nondepleting anti-NKG2D monoclonal antibody (mAb) during the prediabetic stage completely prevented disease by impairing the expansion and function of autoreactive CD8(+) T cells. These findings demonstrate that NKG2D is essential for disease progression and suggest a new therapeutic target for autoimmune type I diabetes.

Adoptive Transfer↗
PubMed2004

IL-1 receptor deficiency slows progression to diabetes in the NOD mouse.

Proinflammatory cytokines are believed to be important in pancreatic beta-cell destruction in the development of type 1 diabetes. They act by upregulation of genes including Fas and inducible nitric oxide synthase (iNOS), which have both been shown to lead to beta-cell death in vitro. We used mice deficient in the interleukin (IL)-1 receptor (IL-1R) to assess the contribution of IL-1 to different models of diabetes. IL-1R-deficient islets were protected from the damaging effects of tumor necrosis factor (TNF) and interferon (IFN)-gamma in vitro, and beta-cell expression of iNOS was reduced, suggesting that IL-1 mediates the induction of iNOS by TNF and IFN-gamma. IL-1 action was not required for induction of class I major histocompatibility complex or Fas by TNF and IFN-gamma. IL-1R-deficient nonobese diabetic (NOD) mice developed diabetes significantly slower than wild-type mice. IL-1R deficiency did not affect diabetes in 8.3 TCR transgenic NOD mice but prolonged the time to diabetes in BDC2.5 TCR transgenic NOD mice. We conclude that IL-1R deficiency slows progression to diabetes in NOD mice but on its own does not prevent diabetes.

Animals↗
PubMed2004

Tracking the recruitment of diabetogenic CD8+ T-cells to the pancreas in real time.

Development of autoimmune diabetes in both humans and mice is preceded by a prolonged period of inflammation of pancreatic islets by autoreactive T-cells. Noninvasive imaging techniques, including positron-emission tomography and optical or magnetic resonance imaging, have been used to track the recruitment of lymphocytes to sites of inflammation. These techniques, however, rely on labeling strategies that are non-antigen specific and do not allow specific tracking of the recruitment of autoreactive lymphocytes. Here we describe an antigen-specific magnetic label to selectively target a prevalent population of diabetogenic CD8(+) T-cells that contribute to the progression of insulitis to overt diabetes in NOD mice. Superparamagnetic nanoparticles coated with multiple copies of a high-avidity peptide/major histocompatibility complex ligand of these T-cells (NRP-V7/K(d)) are endocytosed by CD8(+) T-cells in an antigen-specific manner. Using these T-cells as probes, we show that inflammation of pancreatic islets by autoreactive T-cells can be detected in real time by magnetic resonance imaging. This study demonstrates the feasibility of visualizing the presence of ongoing autoimmune responses noninvasively.

Animals↗
PubMed2003

Cross-priming of diabetogenic T cells dissociated from CTL-induced shedding of beta cell autoantigens.

Cross-presentation of self Ags by APCs is key to the initiation of organ-specific autoimmunity. As MHC class I molecules are essential for the initiation of diabetes in nonobese diabetic (NOD) mice, we sought to determine whether the initial insult that allows cross-presentation of beta cell autoantigens in diabetes is caused by cognate interactions between naive CD8(+) T cells and beta cells. Naive splenic CD8(+) T cells from transgenic NOD mice expressing a diabetogenic TCR killed peptide-pulsed targets in the absence of APCs. To ascertain the role of CD8(+) T cell-induced beta cell lysis in the initiation of diabetes, we expressed a rat insulin promoter (RIP)-driven adenovirus E19 transgene in NOD mice. RIP-E19 expression inhibited MHC class I transport exclusively in beta cells and rendered these cells resistant to lysis by CD8(+) (but not CD4(+)) T cells, both in vitro and in vivo. Surprisingly, RIP-E19 expression impaired the accumulation of CD8(+) T cells in islets and delayed the onset of islet inflammation, without affecting the timing or magnitude of T cell cross-priming in the pancreatic lymph nodes, which is the earliest known event in diabetogenesis. These results suggest that access of beta cell autoantigens to the cross-presentation pathway in diabetes is T cell independent, and reveal a previously unrecognized function of MHC class I molecules on target cells in autoimmunity: local retention of disease-initiating clonotypes.

Animals↗
PubMed2003

Identification of the beta cell antigen targeted by a prevalent population of pathogenic CD8+ T cells in autoimmune diabetes.

Type 1 diabetes is an autoimmune disease in which autoreactive T cells attack and destroy the insulin-producing pancreatic beta cells. CD8+ T cells are essential for this beta cell destruction, yet their specific antigenic targets are largely unknown. Here, we reveal that the autoantigen targeted by a prevalent population of pathogenic CD8+ T cells in nonobese diabetic mice is islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP). Through tetramer technology, IGRP-reactive T cells are readily detected in islets and peripheral blood directly ex vivo. The human IGRP gene maps to a diabetes susceptibility locus, suggesting that IGRP also may be an antigen for pathogenic T cells in human type 1 diabetes and, thus, a new, potential target for diagnostic and therapeutic approaches.

Animals↗
PubMed2003

Fas is detectable on beta cells in accelerated, but not spontaneous, diabetes in nonobese diabetic mice.

Fas (CD95) is a potential mechanism of pancreatic beta cell death in type 1 diabetes. beta cells do not constitutively express Fas but it is induced by cytokines. The hypothesis of this study is that Fas expression should be measurable on beta cells for them to be killed by this mechanism. We have previously reported that up to 5% of beta cells isolated from nonobese diabetic (NOD) mice are positive for Fas expression by flow cytometry using autofluorescence to identify beta cells. We have now found that these are not beta cells but contaminating dendritic cells, macrophages, and B lymphocytes. In contrast beta cells isolated from NODscid mice that are recipients of T lymphocytes from diabetic NOD mice express Fas 18-25 days after adoptive transfer but before development of diabetes. Fas expression on beta cells was also observed in BDC2.5, 8.3, and 4.1 TCR-transgenic models of diabetes in which diabetes occurs more rapidly than in unmodified NOD mice. In conclusion, Fas is observed on beta cells in models of diabetes in which rapid beta cell destruction occurs. Its expression is likely to reflect differences in the intraislet cytokine environment compared with the spontaneous model and may indicate a role for this pathway in beta cell destruction in rapidly progressive models.

Animals↗
PubMed2003

Autoimmune islet destruction in spontaneous type 1 diabetes is not beta-cell exclusive.

Pancreatic islets of Langerhans are enveloped by peri-islet Schwann cells (pSC), which express glial fibrillary acidic protein (GFAP) and S100beta. pSC-autoreactive T- and B-cell responses arise in 3- to 4-week-old diabetes-prone non-obese diabetic (NOD) mice, followed by progressive pSC destruction before detectable beta-cell death. Humans with probable prediabetes generate similar autoreactivities, and autoantibodies in islet-cell autoantibody (lCA) -positive sera co-localize to pSC. Moreover, GFAP-specific NOD T-cell lines transferred pathogenic peri-insulitis to NOD/severe combined immunodeficient (NOD/SCID) mice, and immunotherapy with GFAP or S100beta prevented diabetes. pSC survived in rat insulin promoter Iymphocytic choriomeningitis virus (rip-LCMV) glycoprotein/CD8+ T-cell receptor(gp) double-transgenic mice with virus-induced diabetes, suggesting that pSC death is not an obligate consequence of local inflammation and beta-cell destruction. However, pSC were deleted in spontaneously diabetic NOD mice carrying the CD8+/8.3 T-cell receptor transgene, a T cell receptor commonly expressed in earliest islet infiltrates. Autoimmune targeting of pancreatic nervous system tissue elements seems to be an integral, early part of natural type 1 diabetes.

Animals↗
PubMed2003

CD40 ligation releases immature dendritic cells from the control of regulatory CD4+CD25+ T cells.

We report that disruption of CD154 in nonobese diabetic (NOD) mice abrogates the helper function of CD4+CD25- T cells without impairing the regulatory activity of CD4+CD25+ T cells. Whereas CD4+ T cells from NOD mice enhanced a diabetogenic CD8+ T cell response in monoclonal TCR-transgenic NOD mice, CD4+ T cells from NOD.CD154(-/-) mice actively suppressed it. Suppression was mediated by regulatory CD4+CD25+ T cells capable of inhibiting CD8+ T cell responses induced by peptide-pulsed dendritic cells (DCs), but not peptide/MHC monomers. It involved inhibition of DC maturation, did not occur in the presence of CD154+ T-helper cells, and could be inhibited by activation of DCs with LPS, CpG DNA, or an agonistic anti-CD40 mAb. Thus, in at least some genetic backgrounds, CD154-CD40 interactions and innate stimuli release immature DCs from suppression by CD4+CD25+ T cells.

Animals↗
PubMed2003

Prediction of spontaneous autoimmune diabetes in NOD mice by quantification of autoreactive T cells in peripheral blood.

Autoimmune (type 1) diabetes mellitus results from the destruction of insulin-producing pancreatic beta cells by T lymphocytes. Prediction of cell-mediated autoimmune diseases by direct detection of autoreactive T cells in peripheral blood has proved elusive, in part because of their low frequency and reduced avidity for peptide MHC ligands. This article was published online in advance of the print edition. The date of publication is available from the JCI website, http://www.jci.org.

Animals↗
PubMed2003

Kinetic evolution of a diabetogenic CD8+ T cell response.

Nonobese diabetic (NOD) mice develop overt diabetes following prolonged periods of pancreatic islet inflammation involving both CD4+ and CD8+ T cells. The initiation and progression of autoimmune diabetes require the recruitment of beta cell-reactive CD8+ T cells to the pancreatic lymph nodes, their activation by antigen, and their subsequent migration into pancreatic islets. We and others have shown that a significant fraction of NOD islet-associated CD8+ T cells express highly homologous TCRalpha chains (Valpha17 and Jalpha42 joined by the same N-region sequence) and that they recognize the peptide NRP-A7 in the context of the MHC class I molecule H-2K(d). We have also shown that this T cell subpopulation undergoes a process of "avidity maturation" that is associated with progression of benign insulitis to overt diabetes. This paper will summarize our current understanding of the mechanisms that drive the recruitment and activation of this CD8+ T cell subpopulation.

Animals↗
PubMed2002

RAG-dependent peripheral T cell receptor diversification in CD8+ T lymphocytes.

Rearrangement of T cell receptor (TCR) genes is driven by transient expression of V(D)J recombination-activating genes (RAGs) during lymphocyte development. Immunological dogma holds that T cells irreversibly terminate RAG expression before exiting the thymus, and that all of the progeny arising from mature T cells express the parental TCRs. When single pancreatic islet-derived, NRP-A7 peptide-reactive CD8(+) T cells from nonobese diabetic (NOD) mice were repeatedly stimulated with peptide-pulsed dendritic cells, daughter T cells reexpressed RAGs, lost their ability to bind to NRP-A7K(d) tetramers, ceased to transcribe tetramer-specific TCR genes, and, instead, expressed a vast array of other TCR rearrangements. Pancreatic lymph node (PLN) CD8(+) T cells from animals expressing a transgenic NRP-A7-reactive TCR transcribed and translated RAGs in vivo and displayed endogenous TCRs on their surface. RAG reexpression also occurred in the PLN CD8(+) T cells of wild-type NOD mice and could be induced in the peripheral CD8(+) T cells of nondiabetes-prone TCR-transgenic B10.H2(g7) mice by stimulation with peptide-pulsed dendritic cells. In contrast, reexpression of RAGs could not be induced in the CD8(+) T cells of B6 mice expressing an ovalbumin-specific, K(b)-restricted TCR, or in the CD8(+) T cells of NOD mice expressing a lymphocytic choriomeningitis virus-specific, D(b)-restricted TCR. Extra-thymic reexpression of the V(D)J recombination machinery in certain CD8(+) T cell subpopulations, therefore, enables further diversification of the peripheral T cell repertoire.

Animals↗
PubMed2002

Inducible nitric oxide synthase (iNOS) in endotoxemia: chimeric mice reveal different cellular sources in various tissues.

The aim of these experiments was to determine the contribution of leukocyte-derived iNOS to total iNOS expression induced by lipopolysaccharide (LPS). By transferring bone marrow between iNOS+/+ and iNOS-/- mice, we created chimeric mice in which iNOS expression was limited to either circulating leukocytes (leukocyte-iNOS mice) or parenchymal cells (parenchyma-iNOS mice). Analysis of congenic markers demonstrated that >95% of thymocytes in chimeric mice were of donor origin. Also, following LPS treatment, iNOS mRNA was detectable in blood from leukocyte-iNOS mice but not parenchyma-iNOS mice. Together these findings indicated that the host marrow had been replaced entirely by donor cells. In the lung, at least 50% of the LPS-induced iNOS mRNA was derived from leukocytes, and immunohistochemical analysis indicated that leukocytes were the main source of iNOS protein. In contrast in the liver, colon, and muscle, iNOS expression was derived predominantly from parenchymal cells. This divergence is potentially explained by the high level of leukocyte recruitment to the lung, relative to the other tissues. Plasma levels of NOS byproducts indicated that parenchymal iNOS was the dominant source of systemic iNOS activity. These findings indicate that in tissues other than the lung, parenchymal cells are the principal source of iNOS during endotoxemia.

Animals↗
PubMed2002

In situ beta cell death promotes priming of diabetogenic CD8 T lymphocytes.

CTLs are important mediators of pancreatic beta cell destruction in the nonobese diabetic mouse model of type 1 diabetes. Cross-presentation of Ag is one means of priming CTLs. The death of Ag-bearing cells has been implicated in facilitating this mode of priming. The role of beta cell death in facilitating the onset of spontaneous autoimmune diabetes is unknown. Here, we used an adoptive transfer system to determine the time course of islet-derived Ag presentation to naive beta cell-specific CD8 T cells in nonobese diabetic mice and to test the hypothesis that beta cell death enhances the presentation of beta cell autoantigen. We have determined that beta cell death enhances autoantigen presentation. Priming of diabetogenic CD8 T cells in the pancreatic lymph nodes was negligible before 4 wk, progressively increased until 8 wk of age, and was not influenced by gender. Administration of multiple low doses of the beta cell toxin streptozotocin augmented in situ beta cell apoptosis and accelerated the onset and magnitude of autoantigen presentation to naive CD8 T cells. Increasing doses of streptozotocin resulted in both increased pancreatic beta cell death and significantly enhanced T cell priming. These results indicate that in situ beta cell death facilitates autoantigen-specific CD8 T cell priming and can contribute to both the initiation and the ongoing amplification of an autoimmune response.

Adjuvants, Immunologic↗