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Objective: Excess accumulation of advanced glycation end products (AGEs) contributes to aging and chronic diseases. We aimed to obtain evidence that exposure to AGEs plays a role in the development of type 1 diabetes (T1D).Research Design and Methods: The effect of AGEs was examined on insulin secretion by MIN6N8 cells and mouse islets and in vivo in three separate rodent models: AGE-injected or high AGE-fed Sprague-Dawley rats and nonobese diabetic (NODLt) mice. Rodents were also treated with the AGE-lowering agent alagebrium.Results: β-Cells exposed to AGEs displayed acute glucose-stimulated insulin secretory defects, mitochondrial abnormalities including excess superoxide generation, a decline in ATP content, loss of MnSOD activity, reduced calcium flux, and increased glucose uptake, all of which were improved with alagebrium treatment or with MnSOD adenoviral overexpression. Isolated mouse islets exposed to AGEs had decreased glucose-stimulated insulin secretion, increased mitochondrial superoxide production, and depletion of ATP content, which were improved with alagebrium or with MnTBAP, an SOD mimetic. In rats, transient or chronic exposure to AGEs caused progressive insulin secretory defects, superoxide generation, and β-cell death, ameliorated with alagebrium. NODLt mice had increased circulating AGEs in association with an increase in islet mitochondrial superoxide generation, which was prevented by alagebrium, which also reduced the incidence of autoimmune diabetes. Finally, at-risk children who progressed to T1D had higher AGE concentrations than matched nonprogressors.Conclusions: These findings demonstrate that AGEs directly cause insulin secretory defects, most likely by impairing mitochondrial function, which may contribute to the development of T1D. [ABSTRACT FROM AUTHOR]

SummaryPrevious studies have implicated B lymphocytes in the pathogenesis of diabetes in the non-obese diabetic (NOD) mouse. While it is clear that B lymphocytes are necessary, it has not been clear at which stage of disease they play a role; early, late or both. To clarify when B lymphocytes are needed, T lymphocytes were transferred from 5-week-old NOD female mice to age-matched NOD/severe combined immunodeficiency (SCID) recipient mice. NOD/SCID mice, which lack functionally mature T and B lymphocytes, do not normally develop insulitis or insulin-dependent diabetes melitus (IDDM). The NOD/SCID mice that received purified T lymphocytes from 5-week-old NOD mice subsequently developed insulitis and diabetes even though they did not have detectable B lymphocytes. This suggests that while B lymphocytes may be essential for an initial priming event they are not requisite for disease progression in the NOD mouse. [ABSTRACT FROM AUTHOR]

Type 1 Diabetes (T1D) is an autoimmune disease in which insulin producing beta cells of the pancreas are selectively destroyed. Glial Fibrillary Acidic Protein (GFAP) expressed in peri-islet Schwann cells (pSCs) and in the ductal cells of the pancreas is one of the candidate autoantigens for T1D. Immune responses to GFAP expressing cell types precede the islet autoimmunity in Non-Obese Diabetic (NOD) mice. By removing MHC class I from GFAP expressing cell types, we tested the role of autoantigens presented by these cell types in the development of invasive insulitis. Our findings indicate that antigens expressed by pancreatic ductal cells are important in the development of invasive insulitis in NOD mice., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The contribution of environmental factors to pancreatic islet damage in type 1 diabetes remains poorly understood. In this study, we crossed mice susceptible to type 1 diabetes, where parental male (CD8 + T cells specific for IGRP 206-214 ; NOD8.3) and female (NOD/ShiLt) mice were randomized to a diet either low or high in AGE content and maintained on this diet throughout pregnancy and lactation. After weaning, NOD8.3 + female offspring were identified and maintained on the same parental feeding regimen for until day 28 of life. A low AGE diet, from conception to early postnatal life, decreased circulating AGE concentrations in the female offspring when compared to a high AGE diet. Insulin, proinsulin and glucagon secretion were greater in islets isolated from offspring in the low AGE diet group, which was akin to age matched non-diabetic C57BL/6 mice. Pancreatic islet expression of Ins2 gene was also higher in offspring from the low AGE diet group. Islet expression of glucagon, AGEs and the AGE receptor RAGE, were each reduced in low AGE fed offspring. Islet immune cell infiltration was also decreased in offspring exposed to a low AGE diet. Within pancreatic lymph nodes and spleen, the proportions of CD4 + and CD8 + T cells did not differ between groups. There were no significant changes in body weight, fasting glucose or glycemic hormones. This study demonstrates that reducing exposure to dietary AGEs throughout gestation, lactation and early postnatal life may benefit pancreatic islet secretion and immune infiltration in the type 1 diabetic susceptible mouse strain, NOD8.3.

The gut microbiota contributes to the development of normal immunity but, when dysregulated, can promote autoimmunity through various non-antigen-specific effects on pathogenic and regulatory lymphocytes. Here, we show that an integrase expressed by several species of the gut microbial genus Bacteroides encodes a low-avidity mimotope of the pancreatic β cell autoantigen islet-specific glucose-6-phosphatase-catalytic-subunit-related protein (IGRP 206-214 ). Studies in germ-free mice monocolonized with integrase-competent, integrase-deficient, and integrase-transgenic Bacteroides demonstrate that the microbial epitope promotes the recruitment of diabetogenic CD8+ T cells to the gut. There, these effectors suppress colitis by targeting microbial antigen-loaded, antigen-presenting cells in an integrin β7-, perforin-, and major histocompatibility complex class I-dependent manner. Like their murine counterparts, human peripheral blood T cells also recognize Bacteroides integrase. These data suggest that gut microbial antigen-specific cytotoxic T cells may have therapeutic value in inflammatory bowel disease and unearth molecular mimicry as a novel mechanism by which the gut microbiota can regulate normal immune homeostasis. PAPERCLIP., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Many pathogens, including the malaria parasite Plasmodium falciparum , display high levels of polymorphism within T-cell epitope regions of proteins associated with protective immunity. The T-cell epitope variants are often non-cross-reactive. Herein, we show in a murine model, which modifies a protective CD8 T-cell epitope from the circumsporozoite protein (CS) of Plasmodium berghei (SYIPSAEKI), that simultaneous or sequential co-stimulation with two of its putative similarly non-cross-reactive altered peptide ligand (APL) epitopes (SYIPSAEDI or SYIPSAEAI) has radically different effects on immunity. Hence, co-immunization or sequential stimulation in vivo of SYIPSAEKI with its APL antagonist SYIPSAEDI decreases immunity to both epitopes. By contrast, co-immunization with SYIPSAEAI has no apparent initial effect, but it renders the immune response to SYIPSAEKI resistant to being turned off by subsequent immunization with SYIPSAEDI. These results suggest a novel strategy for vaccines that target polymorphic epitopes potentially capable of mutual immune interference in the field, by initiating an immune response by co-immunization with the desired index epitope, together with a carefully selected "potentiator" APL peptide.

The properties of CD4(+) regulatory T cell (Treg) subsets are dictated by distinct patterns of gene expression determined by FOXP3 and different combinations of various transcription factors. Here we show the NF-κB transcription factor RelA is constitutively active in naïve and effector Tregs. The conditional inactivation of Rela in murine FOXP3(+) cells induces a rapid onset, multi-focal autoimmune disease that depends on RelA being expressed in conventional T cells. In addition to promoting Treg lineage stability, RelA determines the size of the effector Treg population, a function influenced by the presence or absence of RelA in conventional T cells. These findings showing that RelA controls Treg stability and promotes the competitive fitness of effector Tregs highlight the importance of RelA activity in peripheral Treg induced tolerance., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In type 1 diabetes, cytotoxic CD8(+) T lymphocytes (CTLs) directly interact with pancreatic beta cells through major histocompatibility complex class I. An immune synapse facilitates delivery of cytotoxic granules, comprised mainly of granzymes and perforin. Perforin deficiency protects the majority of non-obese diabetic (NOD) mice from autoimmune diabetes. Intriguingly perforin deficiency does not prevent diabetes in CD8(+) T-cell receptor transgenic NOD8.3 mice. We therefore investigated the importance of perforin-dependent killing via CTL-beta cell contact in autoimmune diabetes. Perforin-deficient CTL from NOD mice or from NOD8.3 mice were significantly less efficient at adoptive transfer of autoimmune diabetes into NODRag1(-/-) mice, confirming that perforin is essential to facilitate beta cell destruction. However, increasing the number of transferred in vitro-activated perforin-deficient 8.3 T cells reversed the phenotype and resulted in diabetes. Perforin-deficient NOD8.3 T cells were present in increased proportion in islets, and proliferated more in response to antigen in vivo indicating that perforin may regulate the activation of CTLs, possibly by controlling cytokine production. This was confirmed when we examined the requirement for direct interaction between beta cells and CD8(+) T cells in NOD8.3 mice, in which beta cells specifically lack major histocompatibility complex (MHC) class I through conditional deletion of β2-microglobulin. Although diabetes was significantly reduced, 40% of these mice developed diabetes, indicating that NOD8.3 T cells can kill beta cells in the absence of direct interaction. Our data indicate that although perforin delivery is the main mechanism that CTL use to destroy beta cells, they can employ alternative mechanisms to induce diabetes in a perforin-independent manner.

T1D (Type 1 diabetes) is an autoimmune disease caused by the immune-mediated destruction of pancreatic β-cells. Studies in T1D patients have been limited by the availability of pancreatic samples, a protracted pre-diabetic phase and limitations in markers that reflect β-cell mass and function. The NOD (non-obese diabetic) mouse is currently the best available animal model of T1D, since it develops disease spontaneously and shares many genetic and immunopathogenic features with human T1D. Consequently, the NOD mouse has been extensively studied and has made a tremendous contribution to our understanding of human T1D. The present review summarizes the key lessons from NOD mouse studies concerning the genetic susceptibility, aetiology and immunopathogenic mechanisms that contribute to autoimmune destruction of β-cells. Finally, we summarize the potential and limitations of immunotherapeutic strategies, successful in NOD mice, now being trialled in T1D patients and individuals at risk of developing T1D.

Aims/hypothesis: Type 1 diabetes is characterised by early peri-islet insulitis and insulin autoantibodies, followed by invasive insulitis and beta cell destruction. The immunological events that precipitate invasive insulitis are not well understood. We tested the hypothesis that B cells in diabetes-prone NOD mice drive invasive insulitis through elevated expression of CD19 and consequent enhanced uptake and presentation of beta cell membrane-bound antigens to islet invasive T cells., Methods: CD19 expression and signalling pathways in B cells from NOD and control mice were compared. Expansion of CD8(+) T cells specific for insulin and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) were compared in CD19-deficient and wild-type NOD mice and this was correlated with insulitis severity. The therapeutic potential of anti-CD19 treatment during the period of T cell activation was assessed for its ability to block invasive insulitis., Results: CD19 expression and signalling in B cells was increased in NOD mice. CD19 deficiency significantly diminished the expansion of CD8(+) T cells with specificity for the membrane-bound beta cell antigen, IGRP. Conversely the reduction in CD8(+) T cells with specificity for the soluble beta cell antigen, insulin, was relatively small and not significant., Conclusions/interpretation: Elevated CD19 on NOD B cells promotes presentation of the membrane-bound antigen, IGRP, mediating the expansion of autoreactive T cells specific for antigens integral to beta cells, which are critical for invasive insulitis and diabetes. Downregulating the CD19 signalling pathway in insulin autoantibody-positive individuals before the development of type 1 diabetes may prevent expansion of islet-invasive T cells and preserve beta cell mass.

Several mechanisms have been proposed to explain how certain MHC class II molecules afford dominant resistance to autoimmune diseases like type 1 diabetes (T1D). However, it remains unclear how protective MHC types can blunt autoreactive T cell responses directed against a diverse repertoire of autoantigenic epitopes presented by disease-promoting MHCs. In this study, we show that expression of I-E on dendritic cells (DCs) of NOD mice promotes the differentiation of MHC promiscuous autoreactive CD4(+) clonotypes into antidiabetogenic autoregulatory T cells. We expressed an I-Eα(kloxP) transgene in NOD mice and used cell type-specific I-E ablation to show that I-E-expressing DCs, but not B cells, promote the generation of autoreactive CD4(+)Foxp3(+) regulatory T cells (Tregs) and their accumulation in the pancreas-draining lymph nodes. There, these Tregs suppress the presentation of β cell Ags to naive autoreactive CD4(+) and CD8(+) T cells restricted by diabetogenic MHC molecules in an I-E-independent manner. Whereas selective removal of I-E on DCs abrogated autoregulatory Treg formation and T1D protection, selective removal of I-E on B cells was inconsequential. These results explain how certain MHC class II molecules can completely suppress antigenically complex autoimmune responses in an Ag-nonspecific manner.

Polymorphisms in MHC class II molecules, in particular around β-chain position-57 (β57), afford susceptibility/resistance to multiple autoimmune diseases, including type 1 diabetes, through obscure mechanisms. Here, we show that the antidiabetogenic MHC class II molecule I-A(b) affords diabetes resistance by promoting the differentiation of MHC-promiscuous autoreactive CD4(+) T cells into disease-suppressing natural regulatory T cells, in a β56-67-regulated manner. We compared the tolerogenic and antidiabetogenic properties of CD11c promoter-driven transgenes encoding I-A(b) or a form of I-A(b) carrying residues 56-67 of I-Aβ(g7) (I-A(b-g7)) in wild-type nonobese diabetic (NOD) mice, as well as NOD mice coexpressing a diabetogenic and I-A(g7)-restricted, but MHC-promiscuous T-cell receptor (4.1). Both I-A transgenes protected NOD and 4.1-NOD mice from diabetes. However, whereas I-A(b) induced 4.1-CD4(+) thymocyte deletion and 4.1-CD4(+)Foxp3(+) regulatory T-cell development, I-A(b-g7) promoted 4.1-CD4(+)Foxp3(+) Treg development without inducing clonal deletion. Furthermore, non-T-cell receptor transgenic NOD.CD11cP-I-A(b) and NOD.CD11cP-IA(b-g7) mice both exported regulatory T cells with superior antidiabetogenic properties than wild-type NOD mice. We propose that I-A(b), and possibly other protective MHC class II molecules, afford disease resistance by engaging a naturally occurring constellation of MHC-promiscuous autoreactive T-cell clonotypes, promoting their deviation into autoregulatory T cells.

Infiltration of pancreatic islets by immune cells, termed insulitis, increases progressively once it begins and leads to clinical type 1 diabetes. But even after diagnosis some islets remain unaffected and infiltration is patchy rather than uniform. Traffic of autoreactive T cells into the pancreas is likely to contribute to insulitis progression but it could also depend on T-cell proliferation within islets. This study utilizes transgenic NOD mice to assess the relative contributions of these two mechanisms. Progression of insulitis in NOD8.3 TCR transgenic mice was mildly reduced by inhibition of T-cell migration with the drug FTY720. In FTY720-treated mice, reduced beta cell MHC class I expression prevented progression of insulitis both within affected islets and to previously unaffected islets. CTL proliferation was significantly reduced in islets with reduced or absent beta cell expression of MHC class I protein. This indicates that intra-islet proliferation, apparently dependent on beta cell antigen presentation, in addition to recruitment, is a significant factor in progression of insulitis., (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

CD8(+) T cells kill pancreatic β-cells in a cell-cell contact-dependent mechanism in the non-obese diabetic mouse. CD4(+) T lymphocytes are also able to kill pancreatic β-cells, but they do not directly contact β-cells and may use another cell type as the actual cytotoxic cell. Natural killer (NK) cells could have this role but it is uncertain whether they are cytotoxic towards β-cells. Therefore, the requirement for NK cells in β-cell destruction in the CD4-dependent T-cell antigen receptor transgenic NOD4.1 mice was examined. NK cells failed to kill β-cells in vitro, even in the absence of major histocompatibility complex class I. We observed only 9.7±1.1% of islet infiltrating NK cells from NOD4.1 mice expressing the degranulation marker CD107a. Diabetogenic CD4(+) T cells transferred disease to NODscid.IL2Rγ(-/-) mice lacking NK cells, indicating that NK cells do not contribute to β-cell death in vitro or in vivo. However, depletion of NK cells reduced diabetes incidence in NOD4.1 mice, suggesting that NK cells may help to maintain the right environment for cytotoxicity of effector cells.

Type 1 NKT cells play a critical role in controlling the strength and character of adaptive and innate immune responses. We have previously reported deficiencies in the numbers and function of NKT cells in the NOD mouse strain, which is a well-validated model of type 1 diabetes and systemic lupus erythematosus. Genetic control of thymic NKT cell numbers was mapped to two linkage regions: Nkt1 on distal chromosome 1 and Nkt2 on chromosome 2. Herein, we report the production and characterization of a NOD.Nkrp1(b).Nkt2b(b) congenic mouse strain, which has increased thymic and peripheral NKT cells, a decreased incidence of type 1 diabetes, and enhanced cytokine responses in vivo and increased proliferative responses in vitro following challenge with alpha-galactosylceramide. The 19 highly differentially expressed candidate genes within the congenic region identified by microarray expression analyses included Pxmp4. This gene encodes a peroxisome-associated integral membrane protein whose only known binding partner is Pex19, an intracellular chaperone and component of the peroxisomal membrane insertion machinery encoded by a candidate for the NKT cell control gene Nkt1. These findings raise the possibility that peroxisomes play a role in modulating glycolipid availability for CD1d presentation, thereby influencing NKT cell function.

AIRE (autoimmune regulator) promotes the establishment of self-tolerance by regulating gene expression in the thymus. Mutations in AIRE lead to an autoimmune disease, APECED. Here we have identified PIAS proteins as novel AIRE interaction partners. Although PIAS proteins function as E3 SUMO ligases, AIRE is not sumoylated. We expressed AIRE, wt PIAS1, and PIAS1 mutants with deleted SP-RING domain or SUMO interaction motif (SIM) in different cell lines and demonstrate that AIRE and PIAS1 localize to adjacent nuclear bodies (NBs). The expression of AIRE enhances the formation of PIAS1 NBs. The ability of PIAS1 to localize into NBs and interconnect with AIRE is neither dependent on the SP-RING domain nor the SIM. Further, we show that PIAS1 is able to attract AIRE into SUMO1-containing complexes and that the process is dependent on the SIM of PIAS1. PIAS1 and AIRE concurrently activate the human insulin promoter, a known target gene of AIRE, and the SP-RING is required for this activation. Moreover, AIRE represses and PIAS1 activates the CSTB promoter, used as a model for a housekeeping promoter, and both the SP-RING and SIM are needed for its activation by PIAS1. Collectively, our data suggest that AIRE and PIAS1 interact functionally to regulate the activities of the target genes of AIRE.

Type 1 diabetes (T1D) is caused by the destruction of insulin-producing islet beta cells. CD8 T cells are prevalent in the islets of T1D patients and are the major effectors of beta cell destruction in nonobese diabetic (NOD) mice. In addition to their critical involvement in the late stages of diabetes, CD8 T cells are implicated in the initiation of disease. NOD mice, in which the beta2-microglobulin gene has been inactivated by gene targeting (NOD.beta2M-/-), have a deficiency in CD8 T cells and do not develop insulitis, which suggests that CD8 T cells are required for the initiation of T1D. However, neither in humans nor in NOD mice have the immunological requirements for diabetogenic CD8 T cells been precisely defined. In particular, it is not known in which cell type MHC class I expression is required for recruitment and activation of CD8 T cells. Here we have generated transgenic NOD mice, which lack MHC class I on mature professional antigen-presenting cells (pAPCs). These "class I APC-bald" mice developed periislet insulitis but not invasive intraislet insulitis, and they never became diabetic. Recruitment to the islet milieu does not therefore require cognate interaction between CD8 T cells and MHC class I on mature pAPCs. Conversely, such an interaction is critically essential to allow the crucial shift from periislet insulitis to invasive insulitis. Importantly, our findings demonstrate unequivocally that CD8 T cells cannot be primed to become diabetogenic by islet beta cells alone.

Development of autoreactive CD4 T cells contributing to type 1 diabetes (T1D) in both humans and nonobese diabetic (NOD) mice is either promoted or dominantly inhibited by particular MHC class II variants. In addition, it is now clear that when co-expressed with other susceptibility genes, some common MHC class I variants aberrantly mediate autoreactive CD8 T cell responses also essential to T1D development. However, it was unknown whether the development of diabetogenic CD8 T cells could also be dominantly inhibited by particular MHC variants. We addressed this issue by crossing NOD mice transgenically expressing the TCR from the diabetogenic CD8 T cell clone AI4 with NOD stocks congenic for MHC haplotypes that dominantly inhibit T1D. High numbers of functional AI4 T cells only developed in controls homozygously expressing NOD-derived H2(g7) molecules. In contrast, heterozygous expression of some MHC haplotypes conferring T1D resistance anergized AI4 T cells through decreased TCR (H2(b)) or CD8 expression (H2(q)). Most interestingly, while AI4 T cells exert a class I-restricted effector function, H2(nb1) MHC class II molecules can contribute to their negative selection. These findings provide insights to how particular MHC class I and class II variants interactively regulate the development of diabetogenic T cells and the TCR promiscuity of such autoreactive effectors.

Type 1 diabetes occurs as a result of an autoimmune attack on the insulin-producing beta cells. Although CD8 T cells have been implicated both early and late in this process, the requirement for direct interaction between these cells and MHC class I on the beta cells has not been demonstrated. By using nonobese diabetic mice lacking beta cell class I expression, we show that both initiation and progression of insulitis proceeds unperturbed. However, without beta cell class I expression, the vast majority of these mice do not develop hyperglycemia. These findings demonstrate that a direct interaction between CD8 T cells and beta cells is not required for initiation or early disease progression. The requirement for class I on beta cells is a relatively late checkpoint in the development of diabetes.

Previous studies have implicated B lymphocytes in the pathogenesis of diabetes in the non-obese diabetic (NOD) mouse. While it is clear that B lymphocytes are necessary, it has not been clear at which stage of disease they play a role; early, late or both. To clarify when B lymphocytes are needed, T lymphocytes were transferred from 5-week-old NOD female mice to age-matched NOD/severe combined immunodeficiency (SCID) recipient mice. NOD/SCID mice, which lack functionally mature T and B lymphocytes, do not normally develop insulitis or insulin-dependent diabetes melitus (IDDM). The NOD/SCID mice that received purified T lymphocytes from 5-week-old NOD mice subsequently developed insulitis and diabetes even though they did not have detectable B lymphocytes. This suggests that while B lymphocytes may be essential for an initial priming event they are not requisite for disease progression in the NOD mouse.

Type 1 diabetes in both humans and nonobese diabetic (NOD) mice results from T-cell-mediated autoimmune destruction of insulin-producing pancreatic beta cells. Linkage studies have shown that type 1 diabetes in NOD mice is a polygenic disease involving more than 15 chromosomal susceptibility regions. Despite extensive investigation, the identification of individual susceptibility genes either within or outside the major histocompatibility complex region has proven problematic because of the limitations of linkage analysis. In this paper, we provide evidence implicating a single diabetes susceptibility gene, which lies outside the major histocompatibility complex region. Using allelic reconstitution by transgenic rescue, we show that NOD mice expressing the beta(2) microglobulin (beta(2)M)(a) allele develop diabetes, whereas NOD mice expressing a murine beta(2)M(b) or human allele are protected. The murine beta(2)M(a) allele differs from the beta(2)M(b) allele only at a single amino acid. Mechanistic studies indicate that the absence of the NOD beta(2)M(a) isoform on nonhematopoietic cells inhibits the development or activation of diabetogenic T cells.

CD4+ T cells may be assigned a functional status (Th1 or Th2) according to the cytokines they produce including IL-2, IFN-gamma and IL-4. Th1 and Th2 CD4+ T cells deliver different isotype-switching signals to antigen-specific B cells which bias the serum Ig isotypes. The stimulation of Th1 or Th2 responses is influenced by adjuvants and administration of antigen in IFA results in Th1 unresponsiveness as evidenced by: (i) reduced T cell proliferation to antigen; (ii) reduced IFN-gamma production in response to antigen; and (iii) reduced IgG2a isotype antigen-specific antibodies following antigen/CFA challenge. The impact of established human gamma globulin (HGG) specific Th1 unresponsiveness on subsequent immunization with an unrelated antigen, human serum albumin (HSA) in Th1-inducing CFA was then examined. When subsequently challenged with a mixture of HSA and HGG in CFA the HGG-specific Th1 unresponsiveness was infectious and dominant, preventing the induction of a Th1 response to HSA. Reduced T cell proliferation, IFN-gamma production and IgG2a antibody were consequently observed in response to HSA. The HGG-specific Th1 unresponsiveness was not infectious when HGG/CFA and HSA/CFA were administered at separate sites. This demonstrates that antigen-specific Th1 unresponsiveness can be infectious for new, molecularly unrelated antigens and supports studies showing that Th1-mediated autoimmune diseases such as experimental allergic encephalomyelitis (EAE) and diabetes can be ameliorated using antigens molecularly distinct from the disease-inducing immunogen.

It has been demonstrated recently that neonatal antigen administration in the mouse can lead to priming for Th2-mediated immune responses. This observation has important implications for the development of vaccination strategies in humans, particularly for individuals who may be predisposed to atopy or asthma. In this paper it is shown that although i.p. administration of antigen (100 microg) in adjuvant to the neonate does indeed prime for Th2-mediated disease in mice [allergic airways disease (AAD)], when the same relatively low dose of antigen is given in soluble form no priming occurs. Further, administration of a larger dose of soluble antigen (1 mg) actually prevents the ability to prime for a Th2 response subsequently and so prevents the induction of AAD. Protection from disease was associated with evidence of functional inactivation of both Th1 and Th2 ovalbumin-specific T cells. In contrast, administration of a very low dose of antigen (10 microg) primed for a Th2 response in a similar fashion to antigen in adjuvant. We suggest that the adjuvant lowers the "effective" dose of antigen administered in the neonate and thereby primes for Th2-type immune responses. These findings demonstrate that neonatal antigen administration can inhibit Th2-mediated diseases, such as AAD, but the dose of antigen may be critical to avoid predisposition to disease.

Central to the autoimmune pathogenesis of IDDM in NOD mice is the MHC class II region. In all models studied to date, expression of NOD MHC class II genes is essential for disease development suggesting a crucial role for I-ANOD-restricted presentation of autoantigen. Protection has been afforded by transgene incorporation of other non-NOD class II genes and many models have been proposed to account for this effect. It is now clear that protection is not achieved by deletion or permanent silencing of all autoreactive T cell clones. It also appears that expression of these genes is required both intra- and extrathymically. It still remains to be determined what role these genes may have in the various compartments and how the autoreactive cells are held in check in protected NOD transgenic mice. Currently, the most likely explanation is that intrathymic expression of non-NOD class II genes is required for the positive selection of class II-restricted immunoregulatory T cells, while peripheral expression is necessary to bring about the interaction of these cells in a tricellular complex with NOD autoantigen-specific T cells and APCs, so that the response can be deviated to a nonpathogenetic one. Whether this process is active or passive is not known.

The association of major histocompatibility complex genes with autoimmune diseases is firmly established, but the mechanisms by which these genes confer resistance or susceptibility remain controversial. The controversy extends to the nonobese diabetic (NOD) mouse that develops disease similar to human insulin-dependent diabetes mellitus. The transgenic incorporation of certain class II major histocompatibility complex genes protects NOD mice from diabetes, and clonal deletion or functional silencing of autoreactive T cells has been proposed as the mechanism by which these molecules provide protection. We show that neither thymic deletion nor anergy of autoreactive T cells occurs in NOD mice transgenic for I-Ak. Autoreactive T cells are present, functional, and can transfer diabetes to appropriate NOD-recipient mice.

Antigen specific unresponsiveness can be induced in vivo by administration of antibody against CD4, major histocompatibility complex (MHC) Class II or LFA-1 at the time of antigen exposure. Since target cell depletion is not necessary for this effect it was hypothesized that interference with intercellular interaction was responsible. To test this hypothesis, antibody against the ligand for LFA-1, ICAM-1, was administered during primary immunization with human gamma-globulin (HGG) and long-term secondary antibody responses monitored. It was found that HGG specific unresponsiveness resulted from this treatment (less than 10% of normal secondary antibody response). Delayed-type hypersensitivity responses to HGG were also suppressed suggesting unresponsiveness in some T cell subsets. These findings suggest a role for ICAM-1/LFA-1 interaction in determining the long-term outcome of contact with antigen.

The non-obese diabetic (NOD) mouse develops insulin-dependent diabetes mellitus (IDDM) with mononuclear cell infiltration of the islets of Langerhans and selective destruction of the insulin-producing beta-cells, as in humans. Most infiltrating cells are T lymphocytes, and most of these carry the CD4 antigen. Adoptive transfer of T cells from diabetic NOD mice into irradiated NOD or athymic nude NOD mice induces diabetes. Susceptibility to IDDM in NOD mice is polygenic, with one gene linked to the major histocompatibility complex class II locus, which in NOD mice expresses a unique I-A molecule but no I-E. Speculation exists as to the role of the I-A molecule in the diabetes susceptibility of NOD mice, especially regarding the significance of specific unique residues. To examine the role of the NOD I-A molecule in IDDM pathogenesis, we made NOD/Lt mice transgenic for I-Ak by microinjecting I-Ak alpha- and beta-genes into fertilized NOD/Lt eggs. Insulitis was markedly reduced and diabetes prevented in NOD/Lt mice expressing I-Ak.

Nonobese diabetic (NOD) mice spontaneously develop a lymphocytic infiltration of pancreatic islets (insulitis) that may progress to overt diabetes. Virtually all NOD/WEHI mice develop insulitis, but very few progress to diabetes. However, cyclophosphamide (CY) can promote the onset of diabetes in NOD mice, including the NOD/WEHI strain. The means by which CY produces diabetes was investigated in NOD/WEHI mice, in which it was hypothesized that active suppression mechanisms prevented the progression from insulitis to diabetes. A study of the time course of insulitis in the islets after CY was given showed that insulitis was initially reduced but rapidly increased over 16 days, and T-lymphocytes were predominant in the lesion. This suggested a compression of the normal time course of the disease seen in NOD mice. CY did not produce diabetes in any of 11 non-NOD strains studied. Fetal isografts in NOD mice given CY several days before were subjected to lymphocytic infiltration and beta-cell destruction. These findings suggested that CY was not directly beta-cell toxic and that altered beta-cells were not essential for beta-cell destruction. This was further demonstrated with subdiabetogenic doses of streptozocin, which significantly damaged beta-cells but did not increase the severity of insulitis or induce diabetes as did CY. Most important, the transfer of mononuclear cells from nondiabetic NOD mice to mice given CY prevented diabetes, which indicated that the likely effect of CY was via immunomodulation, possibly by allowing poised effector cells to act on beta-cells.(ABSTRACT TRUNCATED AT 250 WORDS)