Induction of diabetes in nonobese diabetic mice by Th2 T cell clones from a TCR transgenic mouse

We have produced a panel of cloned T cell lines from the BDC-2.5 TCR transgenic (Tg) mouse that exhibit a Th2 cytokine phenotype in vitro but are highly diabetogenic in vivo. Unlike an earlier report in which T cells obtained from the Tg mouse were cultured for 1 wk under Th2-promoting conditions and were found to induce disease only in NOD.scid recipients, we found that long-term T cell clones with a fixed Th2 cytokine profile can transfer disease only to young nonobese diabetic (NOD) mice and never to NOD.scid recipients. Furthermore, the mechanism by which diabetes is transferred by a Tg Th2 T cell clone differs from that of the original CD4+ Th1 BDC-2.5 T cell clone made in this laboratory. Whereas the BDC-2.5 clone rapidly causes disease in NOD.scid recipients less than 2 wk old, the Tg Th2 T cell clones can do so only when cotransferred with other diabetogenic T cells, suggesting that the Th2 T cell requires the presence of host T cells for initiation of disease.     

Beta-cell apoptosis in an accelerated model of autoimmune diabetes.

BACKGROUND: The non-obese diabetic (NOD) mouse is a model of human type 1 diabetes in which autoreactive T cells mediate destruction of pancreatic islet beta cells. Although known to be triggered by cytotoxic T cells, apoptosis has not been unequivocally localized to beta cells in spontaneously diabetic NOD mice. We created a model of accelerated beta-cell destruction mediated by T cells from spontaneously diabetic NOD mice to facilitate the direct detection of apoptosis in beta cells. MATERIALS AND METHODS: NOD.scid (severe combined immunodeficiency) mice were crossed with bm1 mice transgenically expressing the costimulatory molecule B7-1 (CD80) in their beta cells, to generate B7-1 NOD.scid mice. Apoptosis in islet cells was measured as DNA strand breakage by the TdT-mediated-dUTP-nick end labeling (TUNEL) technique. RESULTS: Adoptive transfer of splenocytes from spontaneously diabetic NOD mice into B7-1 NOD.scid mice caused diabetes in recipients within 12-16 days. Mononuclear cell infiltration and apoptosis were significantly greater in the islets of B7-1 NOD.scid mice than in nontransgenic NOD.scid mice. Dual immunolabeling for TUNEL and either B-7 or insulin, or the T cell markers CD4 and CD8, and colocalization by confocal microscopy clearly demonstrated apoptosis in beta cells as well in a relatively larger number of infiltrating T cells. The clearance time of apoptotic beta cells was estimated to be less than 6 min. CONCLUSIONS: B7-1 transgenic beta cells undergo apoptosis during their accelerated destruction in response to NOD mouse effector T cells. Rapid clearance implies that beta cells undergoing apoptosis would be detected only rarely during more protracted disease in spontaneously diabetic NOD mice.     

Blockade of late stages of autoimmune diabetes by inhibition of the receptor for advanced glycation end products

Ligation of the receptor for advanced glycation end products (RAGE) occurs during inflammation. Engagement of RAGE results in enhanced expression of addressins and it is therefore, not surprising that previous studies have shown a role of RAGE/ligand interactions in immune responses including cell/cell contact but the role of RAGE in spontaneous autoimmunity has not been clearly defined. To study the role of RAGE/ligand interactions in autoimmune diabetes, we tested the ability of soluble RAGE, a scavenger of RAGE ligands, in late stages of diabetes development in the NOD mouse-disease transferred with diabetogenic T cells and recurrent disease in NOD/scid recipients of syngeneic islet transplants. RAGE expression was detected on CD4(+), CD8(+), and B cells from diabetic mice and transferred to NOD/scid recipients. RAGE and its ligand, S100B, were found in the islets of NOD/scid mice that developed diabetes. Treatment of recipient NOD/scid mice with soluble RAGE prevented transfer of diabetes and delayed recurrent disease in syngeneic islet transplants. RAGE blockade was associated with increased expression of IL-10 and TGF-beta in the islets from protected mice. RAGE blockade reduced the transfer of disease with enriched T cells, but had no effect when diabetes was transferred with the activated CD4(+) T cell clone, BDC2.5. We conclude that RAGE/ligand interactions are involved in the differentiation of T cells to a mature pathogenic phenotype during the late stages of the development of diabetes.     

B cells promote hepatic inflammation, biliary cyst formation, and salivary gland inflammation in the NOD.c3c4 model of autoimmune cholangitis

There are now several murine models of autoimmune cholangitis that have features both similar and distinct from human PBC. One such model, the NOD.c3c4 mouse, manifests portal cell infiltrates, anti-mitochondrial antibodies but also biliary cysts. The biliary cysts are not a component of PBC and not found in the other murine models. To address the immunopathology in these mice, we generated genetically B cell deficient Igμ^−/− NOD.c3c4 mice and compared the immunopathology of these animals to control B cell sufficient NOD.c3c4 mice. B cell deficient mice demonstrated decreased number of non-B cells in the liver accompanied by reduced numbers of activated natural killer cells. The degree of granuloma formation and bile duct damage were comparable to NOD.c3c4 mice. In contrast, liver inflammation, biliary cyst formation and salivary gland inflammation was significantly attenuated in these B cell deficient mice. In conclusion, B cells play a critical role in promoting liver inflammation and also contribute to cyst formation as well as salivary gland pathology in autoimmune NOD.c3c4 mice, illustrating a critical role of B cells in modulating specific organ pathology and, in particular, in exacerbating both the biliary disease and the sialadenitis.     

CD86 has sustained costimulatory effects on CD8 T cells

CD80 and CD86 both costimulate T cell activation. Their individual effects in vivo are difficult to study as they are coordinately up-regulated on APCs. We have studied mice expressing rat insulin promoter (RIP)-CD80 and RIP-CD86 on the NOD and NOD.scid genetic background to generate in vivo models, using diabetes as a readout for cytotoxic T cell activation. Accelerated spontaneous diabetes onset was observed in NOD-RIP-CD80 mice and the transfer of diabetes from 6-wk-old NOD mice to NOD.scid-RIP-CD80 mice was greater compared with NOD-RIP-CD86 and NOD.scid-RIP-CD86 mice, respectively. However, the secondary in vivo response was maintained if T cells were activated through CD86 costimulation compared with CD80. This was demonstrated by greater ability to cause recurrent diabetes in NOD-RIP-CD86 diabetic mice transplanted with 6-wk-old NOD islets and adoptively transferred diabetes from diabetic NOD-RIP-CD86 mice to NOD.scid mice. In vitro, CD80 costimulation enhanced cytotoxicity, proliferation, and cytokine secretion in activated CD8 T cells compared with CD86 costimulation. We demonstrated increased CTLA-4 and programmed death-1 inhibitory molecule expression following costimulation by both CD80 and CD86 (CD80 > CD86). Furthermore, T cells stimulated by CD80 were more susceptible to inhibition by CD4(+)CD25(+) T cells. Overall, while CD86 does not stimulate an initial response as strongly as CD80, there is greater sustained activity that is seen even in the absence of continued costimulation. These functions have implications for the engineered use of costimulatory molecules in altering immune responses in a therapeutic setting.     

Protection from type 1 diabetes by invariant NK T cells requires the activity of CD4+CD25+ regulatory T cells

Invariant NK T (iNKT) cells regulate immune responses, express NK cell markers and an invariant TCR, and recognize lipid Ags in a CD1d-restricted manner. Previously, we reported that activation of iNKT cells by alpha-galactosylceramide (alpha-GalCer) protects against type 1 diabetes (T1D) in NOD mice via an IL-4-dependent mechanism. To further investigate how iNKT cells protect from T1D, we analyzed whether iNKT cells require the presence of another subset(s) of regulatory T cells (Treg), such as CD4+ CD25+ Treg, for this protection. We found that CD4+ CD25+ T cells from NOD.CD1d(-/-) mice deficient in iNKT cell function similarly in vitro to CD4+ CD25+ T cells from wild-type NOD mice and suppress the proliferation of NOD T responder cells upon alpha-GalCer stimulation. Cotransfer of NOD diabetogenic T cells with CD4+ CD25+ Tregs from NOD mice pretreated with alpha-GalCer demonstrated that activated iNKT cells do not influence the ability of T(regs) to inhibit the transfer of T1D. In contrast, protection from T1D mediated by transfer of activated iNKT cells requires the activity of CD4+ CD25+ T cells, because splenocytes pretreated with alpha-GalCer and then inactivated by anti-CD25 of CD25+ cells did not protect from T1D. Similarly, mice inactivated of CD4+ CD25+ T cells before alpha-GalCer treatment were also not protected from T1D. Our data suggest that CD4+ CD25+ T cells retain their function during iNKT cell activation, and that the activity of CD4+ CD25+ Tregs is required for iNKT cells to transfer protection from T1D.     

Natural killer cells in the thymus. Studies in mice with severe combined immune deficiency

The relationship between NK cell and T cell progenitors was investigated by using mice with severe combined immune deficiency (scid). Scid mice are devoid of mature T and B cells because they cannot rearrange their Ig and TCR genes. However, they have normal splenic NK cells. Thymus of scid mice, although markedly hypocellular, contains cells that lyse YAC-1, an NK-sensitive tumor cell. By flow cytometry, two populations of cells were identified in the scid thymus. Eighty percent of the cells were Thy-1+, IL-2R(7D4)+, J11d+, CD3-, CD4-, CD8- whereas the remaining were IL-2R-, J11d-, CD3-, CD4-, and CD8-. By cell sorting, all NK activity was found in the latter population, which is phenotypically similar to splenic NK cells. To determine if the thymus contains a bipotential NK/T progenitor cell, J11d+, IL-2R+ cells were cultured and analyzed for the generation of NK cells in vitro. These cells were used because they resemble 15-day fetal and adult CD4- CD8- thymocytes that are capable of giving rise to mature T cells. Cultured J11d+ thymocytes acquired non-MHC-restricted cytotoxicity, but in contrast to mature NK cells, the resulting cells contained mRNA for the gamma, delta, and epsilon-chains of CD3. This suggests that J11d+ cells are early T cells that can acquire the ability to kill in a non-MHC-restricted manner, but which do not give rise to NK cells in vitro. The differentiative potential of scid thymocytes was also tested in vivo. Unlike bone marrow cells, scid thymocytes containing 80% J11d+ cells failed to give rise to NK cells when transferred into irradiated recipients. Together these results suggest that mature NK cells reside in the thymus of scid mice but are not derived from a common NK/T progenitor.     

Dysregulated B7-1 and B7-2 expression on nonobese diabetic mouse B cells is associated with increased T cell costimulation and the development of insulitis

Little is known about the pathogenic role of B cell dysfunction in T cell-mediated autoimmune disease. We previously reported that B cell hyper-responsiveness, resistance to apoptosis, and accumulation in islets occur during the onset of insulitis, but not in type 1 diabetes (T1D), in NOD mice. In this study we extended these studies to further determine how islet-infiltrated B cells contribute to this inflammatory insulitis. We demonstrate the presence of an increased percentage of B7-1(+) and a decreased percentage of B7-2(+) B cells in the spleen of autoimmune disease-prone NOD and nonobese diabetes-resistant mice compared with the spleen of nonautoimmune disease-prone C57BL/6 and BALB/c mice. An age-dependent differential expression of B7-1 and B7-2 was associated with the development of insulitis and CD4(+)CD25(+) T cell deficiency in autoimmune disease-prone mice. Whereas BCR and LPS stimulation increased B7-2 expression on B cells from autoimmune disease-prone and nonautoimmune disease-prone mice, LPS-induced B7-1 expression was higher on NOD than C57BL/6 B cells. Interestingly, increased expression of B7-1 and B7-2 was found on islet-infiltrated B cells, and this increase was associated with enhanced T cell costimulation. Islet-infiltrated B cells were shown to be a source of TNF-alpha production in islets. B7 blockade of BCR-stimulated NOD B cells by anti-B7-1 and anti-B7-2 mAbs during coadoptive transfer with diabetogenic T cells into NOD.scid mice protected these recipients from T1D. These results suggest that increased B7-1 and B7-2 expression on islet-infiltrated NOD B cells is associated with increased T cell costimulation and the development of inflammatory insulitis in NOD mice.     

Loss of invariant chain protects nonobese diabetic mice against type 1 diabetes

The invariant (Ii) chain acts as an essential chaperone to promote MHC class II surface expression, Ag presentation, and selection of CD4(+) T cells. We have examined its role in the development of type 1 diabetes in NOD mice and show that Ii chain-deficient NOD mice fail to develop type 1 diabetes. Surprisingly, Ii chain functional loss fails to disrupt in vitro presentation of islet Ags, in the context of NOD I-A(g7) molecules. Moreover, pathogenic effector cells could be shown to be present in Ii chain-deficient NOD mice because they were able to transfer diabetes to NOD.scid recipients. The ability of these cells to transfer diabetes was markedly enhanced by depletion of CD25 cells coupled with in vivo anti-CD25 treatment of recipient mice. The numbers of CD4(+)CD25(+)Foxp3(+) T cells in thymus and periphery of Ii chain-deficient NOD mice were similar to those found in normal NOD mice, in contrast to conventional CD4(+) T cells whose numbers were reduced. This suggests that regulatory T cells are unaffected in their selection and survival by the absence of Ii chain and that an alteration in the balance of effector to regulatory T cells contributes to diabetes prevention.     

CD38 is required for the peripheral survival of immunotolerogenic CD4+ invariant NK T cells in nonobese diabetic mice

T cell-mediated autoimmune type-1 diabetes (T1D) in NOD mice partly results from this strain's numerical and functional defects in invariant NK T (iNKT) cells. T1D is inhibited in NOD mice treated with the iNKT cell superagonist alpha-galactosylceramide through a process involving enhanced accumulation of immunotolerogenic dendritic cells in pancreatic lymph nodes. Conversely, T1D is accelerated in NOD mice lacking CD38 molecules that play a role in dendritic cell migration to inflamed tissues. Unlike in standard NOD mice, alpha-galactosylceramide pretreatment did not protect the CD38-deficient stock from T1D induced by an adoptively transferred pancreatic beta cell-autoreactive CD8 T cell clone (AI4). We found that in the absence of CD38, ADP-ribosyltransferase 2 preferentially activates apoptotic deletion of peripheral iNKT cells, especially the CD4+ subset. Therefore, this study documents a previously unrecognized role for CD38 in maintaining survival of an iNKT cell subset that preferentially contributes to the maintenance of immunological tolerance.     

Defective CD8+ T cell peripheral tolerance in nonobese diabetic mice.

Nonobese diabetic (NOD) mice develop spontaneous autoimmune diabetes that involves participation of both CD4+ and CD8+ T cells. Previous studies have demonstrated spontaneous reactivity to self-Ags within the CD4+ T cell compartment in this strain. Whether CD8+ T cells in NOD mice achieve and maintain tolerance to self-Ags has not previously been evaluated. To investigate this issue, we have assessed the extent of tolerance to a model pancreatic Ag, the hemagglutinin (HA) molecule of influenza virus, that is transgenically expressed by pancreatic islet beta cells in InsHA mice. Previous studies have demonstrated that BALB/c and B10.D2 mice that express this transgene exhibit tolerance of HA and retain only low-avidity CD8+ T cells specific for the dominant peptide epitope of HA. In this study, we present data that demonstrate a deficiency in peripheral tolerance within the CD8+ T cell repertoire of NOD-InsHA mice. CD8+ T cells can be obtained from NOD-InsHA mice that exhibit high avidity for HA, as measured by tetramer (K(d)HA) binding and dose titration analysis. Significantly, these autoreactive CD8+ T cells can cause diabetes very rapidly upon adoptive transfer into NOD-InsHA recipient mice. The data presented demonstrate a retention in the repertoire of CD8+ T cells with high avidity for islet Ags that could contribute to autoimmune diabetes in NOD mice.     

Identification of a CD8 T cell that can independently mediate autoimmune diabetes development in the complete absence of CD4 T cell helper functions

Previous work has indicated that an important component for the initiation of autoimmune insulin-dependent diabetes mellitus (IDDM) in the NOD mouse model entails MHC class I-restricted CD8 T cell responses against pancreatic beta cell Ags. However, unless previously activated in vitro, such CD8 T cells have previously been thought to require helper functions provided by MHC class II-restricted CD4 T cells to exert their full diabetogenic effects. In this study, we show that IDDM development is greatly accelerated in a stock of NOD mice expressing TCR transgenes derived from a MHC class I-restricted CD8 T cell clone (designated AI4) previously found to contribute to the earliest preclinical stages of pancreatic beta cell destruction. Importantly, these TCR transgenic NOD mice (designated NOD.AI4alphabeta Tg) continued to develop IDDM at a greatly accelerated rate when residual CD4 helper T cells were eliminated by introduction of the scid mutation or a functionally inactivated CD4 allele. In a previously described stock of NOD mice expressing TCR transgenes derived from another MHC class I-restricted beta cell autoreactive T cell clone, IDDM development was retarded by elimination of residual CD4 T cells. Hence, there is variability in the helper dependence of CD8 T cells contributing to the development of autoimmune IDDM. The AI4 clonotype represents the first CD8 T cell with a demonstrated ability to progress from a naive to functionally activated state and rapidly mediate autoimmune IDDM development in the complete absence of CD4 T cell helper functions.     

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.     

L-selectin is not required for T cell-mediated autoimmune diabetes

Administration of anti-L-selectin (CD62L) mAb to neonatal nonobese diabetic (NOD) mice mediates long term protection against the development of insulitis and overt diabetes. These results suggested that CD62L has a key role in the general function of beta cell-specific T cells. To further examine the role of CD62L in the development of type 1 diabetes, NOD mice lacking CD62L were established. The onset and frequency of overt diabetes were equivalent among CD62L(+/+), CD62L(+/-), and CD62L(-/-) NOD littermates. Furthermore, patterns of T cell activation, migration, and beta cell-specific reactivity were similar in NOD mice of all three genotypes. Adoptive transfer experiments with CD62L(-/-) CD4(+) T cells prepared from BDC2.5 TCR transgenic mice revealed no apparent defects in migration to pancreatic lymph nodes, proliferation in response to beta cell Ag, or induction of diabetes in NOD.scid recipients. In conclusion, CD62L expression is not essential for the development of type 1 diabetes in NOD mice.     

Defective thymic T cell activation by concanavalin A and anti-CD3 in autoimmune nonobese diabetic mice. Evidence for thymic T cell anergy that correlates with the onset of insulitis.

In nonobese diabetic (NOD) mice, T cells play a major role in mediating autoimmunity against pancreatic islet beta-cells. We and others previously reported that age-related alterations in the thymic and peripheral T cell repertoire and function occur in prediabetic NOD mice. To study the mechanism responsible for these T cell alterations, we examined whether a defect exists in the thymus of NOD mice at the level of TCR-mediated signaling after activation by Con A and anti-CD3. We found that thymocytes from NOD mice respond weakly to Con A- and anti-CD3-induced proliferation, compared with thymocytes from control BALB/c, BALB.B, (BALB.B x BALB.K)F1, C57BL/6, and nonobese non-diabetic mice. This defect correlates with the onset of insulitis, because it can be detected at 7 to 8 weeks of age, whereas younger mice displayed a normal T cell responsiveness. Thymic T cells from (NOD x BALB/c)F1 mice, which are insulitis- and diabetes-free, exhibit an intermediate stage of unresponsiveness. This T cell defect is not due to a difference in the level of CD3 and IL-2R expression by NOD and BALB/c thymocytes, and both NOD CD4+ CD8- and CD4- CD8+ mature thymic T cells respond poorly to Con A. BALB/c but not NOD thymic T cells respond to Con A in the presence of either BALB/c or NOD thymic APC, suggesting that the thymic T cell defect in NOD mice is intrinsic to NOD thymic T cells and is not due to an inability of NOD APC to provide a costimulatory signal. The defect can be partially reversed by the addition of rIL-2 to NOD thymocytes. To determine whether a defect in signal transduction mediates this NOD thymic T cell unresponsiveness, we tested whether these cells elevate their intracellular free Ca2+ ion concentration in response to Con A. An equivalent Con A-induced increase in Ca2+ ion concentration in both NOD and BALB/c thymocytes was observed, suggesting a normal coupling between the CD3 complex and phospholipase C in NOD thymocytes. In contrast to their low proliferative response to Con A or anti-CD3, NOD thymocytes respond normally (i.e., as do BALB/c thymocytes) to the combinations of PMA plus the Ca2+ ionophore ionomycin and PMA plus Con A but weakly to Con A plus ionomycin. Our data suggest that the age-related NOD thymocyte unresponsiveness to Con A and anti-CD3 results from a defect in the signaling pathway of T cell activation that occurs upstream of protein kinase C activation.     

Genetic control of autoimmunity: protection from diabetes, but spontaneous autoimmune biliary disease in a nonobese diabetic congenic strain

At least 20 insulin-dependent diabetes (Idd) loci modify the progression of autoimmune diabetes in the NOD mouse, an animal model of human type 1 diabetes. The NOD.c3c4 congenic mouse, which has multiple B6- and B10-derived Idd-resistant alleles on chromosomes 3 and 4, respectively, is completely protected from autoimmune diabetes. We demonstrate in this study, however, that NOD.c3c4 mice develop a novel spontaneous and fatal autoimmune polycystic biliary tract disease, with lymphocytic peribiliary infiltrates and autoantibodies. Strains having a subset of the Idd-resistant alleles present in the NOD.c3c4 strain show component phenotypes of the liver disease: NOD mice with B6 resistance alleles only on chromosome 3 have lymphocytic liver infiltration without autoantibody formation, while NOD mice with B10 resistance alleles only on chromosome 4 show autoantibody formation without liver infiltration. The liver disease is transferable to naive NOD.c3c4 recipients using splenocytes from affected NOD.c3c4 mice, demonstrating an autoimmune etiology. Thus, substitution of non-NOD genetic intervals into the NOD strain can prevent diabetes, but in turn cause an entirely different autoimmune syndrome, a finding consistent with a generalized failure of self-tolerance in the NOD genetic background. The complex clinical phenotypes in human autoimmune conditions may be similarly resolved into largely overlapping biochemical pathways that are then modified, potentially by alleles at a few key chromosomal regions, to produce specific autoimmune syndromes.     

Pancreatic infiltration but not diabetes occurs in the relative absence of MHC class II-restricted CD4 T cells: studies using NOD/CIITA-deficient mice

The NOD (nonobese diabetic) mouse is a good animal model for human IDDM. MHC class II-restricted CD4 T cells are necessary for the onset of diabetes in NOD mice. Here, we demonstrate that NOD mice lacking the CIITA (class II transactivator) molecule, and hence deficient in MHC class II expression and peripheral CD4 T cells, show significant pancreatic infiltration but do not develop diabetes. CD4 T cell deficiency, then, does not prevent initial pancreatic infiltration, but does stop progression to insulitis. Adoptive transfer studies show that the paucity of CD4 T cells in NOD-CIITA knockout mice is responsible for the absence of diabetes, since the CD8 T cell and B cell compartments are functional. An autoaggressive CD8+ T cell clone can, however, transfer diabetes in CIITA knockout recipient mice without CD4 T cell help, albeit with some delay compared with that in CIITA-sufficient recipients. This highlights the fact that a high number of in vitro activated autoaggressive CD8 T cells can over-ride the requirement for CD4 T cell help for the onset of diabetes.     

IL-12, independently of IFN-gamma, plays a crucial role in the pathogenesis of a murine psoriasis-like skin disorder.

The onset of acute psoriasis and the exacerbation of chronic psoriasis are often associated with a history of bacterial infection. We demonstrate that while only few scid/scid mice develop disease when CD4+CD45Rbhigh T cells are transferred alone, coadministration of LPS plus IL-12 or staphylococcal enterotoxin B into scid/scid mice 1 day after CD4+CD45Rbhigh T cell transfer greatly enhances disease penetrance and severity. Most importantly, the skin lesions induced by this method exhibit many of the histologic hallmarks observed in human psoriasis. Skin infiltrating CD4+ T cells were predominantly memory/effector cells (CD45Rblow) and exhibited a highly polarized Th1 phenotype. To test whether the development of pathogenic T cells was dependent on their production of IFN-gamma, we transferred IFN-gamma-/- CD4+CD45Rbhigh T cells into scid/scid or into T, B and NK cell-deficient scid/beige mice. Surprisingly, the incidence of psoriasis was similar to scid/scid animals that received IFN-gamma+/+ T cells, although acanthosis of the skin was attenuated. In contrast, the development of psoriasis was abolished if anti-IL-12 mAb was administered on day 7 and 35 after T cell transfer. Skin-derived IFN-gamma-/- inflammatory cells, but not cells from anti-IL-12-treated animals, secreted substantial amounts of TNF-alpha, suggesting that the inflammatory effect of IFN-gamma-/- T cells may be partly exerted by TNF-alpha and that the therapeutic effect of anti-IL-12 may depend on its ability to down-regulate both TNF-alpha and IFN-gamma. Overall, these results suggest that IL-12, independently of IFN-gamma, is able to induce pathogenic, inflammatory T cells that are able to induce psoriasiform lesions in mice.     

Granulocyte-macrophage colony-stimulating factor prevents diabetes development in NOD mice by inducing tolerogenic dendritic cells that sustain the suppressive function of CD4+CD25+ regulatory T cells

Autoimmune diabetes results from a breakdown of self-tolerance that leads to T cell-mediated beta-cell destruction. Abnormal maturation and other defects of dendritic cells (DCs) have been associated with the development of diabetes. Evidence is accumulating that self-tolerance can be restored and maintained by semimature DCs induced by GM-CSF. We have investigated whether GM-CSF is a valuable strategy to induce semimature DCs, thereby restoring and sustaining tolerance in NOD mice. We found that treatment of prediabetic NOD mice with GM-CSF provided protection against diabetes. The protection was associated with a marked increase in the number of tolerogenic immature splenic DCs and in the number of Foxp3+CD4+CD25+ regulatory T cells (Tregs). Activated DCs from GM-CSF-protected mice expressed lower levels of MHC class II and CD80/CD86 molecules, produced more IL-10 and were less effective in stimulating diabetogenic CD8+ T cells than DCs of PBS-treated NOD mice. Adoptive transfer experiments showed that splenocytes of GM-CSF-protected mice did not transfer diabetes into NOD.SCID recipients. Depletion of CD11c+ DCs before transfer released diabetogenic T cells from the suppressive effect of CD4+CD25+ Tregs, thereby promoting the development of diabetes. These results indicated that semimature DCs were required for the sustained suppressive function of CD4+CD25+ Tregs that were responsible for maintaining tolerance of diabetogenic T cells in NOD mice.