The role of innate immunity in autoimmunity

The Role of Toll-Like Receptors in Retroviral Infection

Toll-like receptors (TLRs) are key pathogen sensing receptors that respond to diverse microbial ligands, and trigger both innate and adaptive immune responses to infection. Since their discovery, a growing body of evidence has pointed to an important role for TLRs in retroviral infection and pathogenesis. These data suggest that multiple TLRs contribute to the anti-retroviral response, and that TLR engagement by retroviruses can have complex and divergent outcomes for infection. Despite this progress, numerous questions remain about the role of TLRs in retroviral infection. In this review, I summarize existing evidence for TLR-retrovirus interactions and the functional roles these receptors play in immunity and pathogenesis, with particular focus on human immunodeficiency virus (HIV).

NOD1 and NOD2 in inflammatory and infectious diseases

It has been long recognized that NOD1 and NOD2 are critical players in the host immune response, primarily by their sensing bacterial peptidoglycan-conserved motifs. Significant advances have been made from efforts that characterize their upstream activators, assembly of signaling complexes, and activation of downstream signaling pathways. Disruption in NOD1 and NOD2 signaling has also been associated with impaired host defense and resistance to the development of inflammatory diseases. In this review, we will describe how NOD1 and NOD2 sense microbes and cellular stress to regulate host responses that can affect disease pathogenesis and outcomes.

Advances in Knowledge of Candidate Genes Acting at the Beta-Cell Level in the Pathogenesis of T1DM

T1DM (type 1 diabetes mellitus), which results from the irreversible elimination of beta-cells mediated by autoreactive T cells, is defined as an autoimmune disease. It is widely accepted that T1DM is caused by a combination of genetic and environmental factors, but the precise underlying molecular mechanisms are still unknown. To date, more than 50 genetic risk regions contributing to the pathogenesis of T1DM have been identified by GWAS (genome-wide association studies). Notably, more than 60% of the identified candidate genes are expressed in islets and beta-cells, which makes it plausible that these genes act at the beta-cell level and play a key role in the pathogenesis of T1DM. In this review, we focus on the current status of candidate genes that act at the beta-cell level by regulating the innate immune response and antiviral activity, affecting susceptibility to proapoptotic stimuli and influencing the pancreatic beta-cell phenotype.

Chronic peripheral inflammation, hippocampal neurogenesis, and behavior

Adult hippocampal neurogenesis is involved in memory and learning, and disrupted neurogenesis is implicated in cognitive impairment and mood disorders, including anxiety and depression. Some long-term peripheral illnesses and metabolic disorders, as well as normal aging, create a state of chronic peripheral inflammation. These conditions are associated with behavioral disturbances linked to disrupted adult hippocampal neurogenesis, such as cognitive impairment, deficits in learning and memory, and depression and anxiety. Pro-inflammatory cytokines released in the periphery are involved in peripheral immune system-to-brain communication by activating resident microglia in the brain. Activated microglia reduce neurogenesis by suppressing neuronal stem cell proliferation, increasing apoptosis of neuronal progenitor cells, and decreasing survival of newly developing neurons and their integration into existing neuronal circuits. In this review, we summarize evolving evidence that the state of chronic peripheral inflammation reduces adult hippocampal neurogenesis, which, in turn, produces the behavioral disturbances observed in chronic inflammatory disorders. As there are no data available on neurogenesis in humans with chronic peripheral inflammatory disease, we focus on animal models and, in parallel, consider the evidence of cognitive disturbance and mood disorders in human patients.

Estrogen Therapy Delays Autoimmune Diabetes and Promotes the Protective Efficiency of Natural Killer T-Cell Activation in Female Nonobese Diabetic Mice

Therapeutic strategies focused on restoring immune tolerance remain the main avenue to prevent type 1 diabetes (T1D). Because estrogens potentiate FoxP3+ regulatory T cells (Treg) and invariant natural killer T (iNKT) cells, two regulatory lymphocyte populations that are functionally deficient in nonobese diabetic (NOD) mice, we investigated whether estradiol (E2) therapy influences the course of T1D in this model. To this end, female NOD mice were sc implanted with E2- or placebo-delivering pellets to explore the course of spontaneous and cyclophosphamide-induced diabetes. Treg-depleted and iNKT-cell-deficient (Jα18(-/-)) NOD mice were used to assess the respective involvement of these lymphocyte populations in E2 effects. Early E2 administration (from 4 wk of age) was found to preserve NOD mice from both spontaneous and cyclophosphamide-induced diabetes, and a complete protection was also observed throughout treatment when E2 treatment was initiated after the onset of insulitis (from 12 wk of age). This delayed E2 treatment remained fully effective in Treg-depleted mice but failed to entirely protect Jα18(-/-) mice. Accordingly, E2 administration was shown to restore the cytokine production of iNKT cells in response to in vivo challenge with the cognate ligand α-galactosylceramide. Finally, transient E2 administration potentiated the previously described protective action of α-galactosylceramide treatment in NOD females. This study provides original evidence that E2 therapy strongly protects NOD mice from T1D and reveals the estrogen/iNKT cell axis as a new effective target to counteract diabetes onset at the stage of insulitis. Estrogen-based therapy should thus be considered for T1D prevention.

Mast cell and autoimmune diseases

Mast cells are important in innate immune system. They have been appreciated as potent contributors to allergic reaction. However, increasing evidence implicates the important role of mast cells in autoimmune disease like rheumatoid arthritis and multiple sclerosis. Here we review the current stage of knowledge about mast cells in autoimmune diseases.

Effects of metalloporphyrins on reducing inflammation and autoimmunity

SIGNIFICANCE

High levels of reactive oxygen species can facilitate DNA and protein damage beyond the control of endogenous antioxidants, resulting in oxidative stress. Oxidative stress then triggers inflammation, which can lead to pathological conditions. In genetically susceptible individuals, the conglomeration of oxidative stress and inflammation can enhance autoreactive immune cell activation, causing beta-cell destruction in autoimmune type 1 diabetes. As a means of shielding pancreatic islets, manganese porphyrin (MnP) oxidoreductant treatment has been tested in a number of reported studies.

RECENT ADVANCES

MnP affects both innate and adaptive immune cell responses, blocking nuclear factor kappa-B activation, proinflammatory cytokine secretion, and T helper 1 T-cell responses. As a result, MnP treatment protects against type 1 diabetes onset in nonobese diabetic mice and stabilizes islets for cellular transplantation.

CRITICAL ISSUES

MnP displays global immunosuppressive properties, exemplified by decreased cytokine production from all T-helper cell subsets. This quality may impact infection control in the setting of autoimmunity. Nonetheless, because of their cytoprotective and immunomodulatory function, MnPs should be considered as a safer alternative to other clinical immunosuppressive agents (i.e., rapamycin) for transplantation.

FUTURE DIRECTIONS

Although MnP likely affects only redox-sensitive targets, the mechanism behind global T-cell immunosuppression and the outcome on infection clearance will have to be elucidated. Based on the increased primary engraftment seen with MnP use, protection against primary nonfunction in porcine to human xenotransplants would likely be enhanced. Further, a better understanding of MnP oxidoreductase function may allow for its use in other chronic inflammatory conditions.

Cross-regulation of T regulatory-cell response after coxsackievirus B3 infection by NKT and γδ T cells in the mouse

Coxsackievirus B3 (CVB3) variants H3 and H310A1 differ by a single nonconserved amino acid in the VP2 capsid region. C57Bl/6 mice infected with the H3 virus develop myocarditis correlating with activation of T cells expressing the Vγ4 T cell receptor chain. Infecting mice with H310A1 activates natural killer T (NKT; mCD1d-tetramer(+) TCRβ(+)) cells, but not Vγ4 T cells, and fails to induce myocarditis. H310A1 infection preferentially activates M2 alternatively activated macrophage and CD4(+)FoxP3 (T regulatory) cells, whereas CD4(+)Th1 (IFN-γ(+)) cells are suppressed. By contrast, H3 virus infection activates M1 proinflammatory and CD4(+)Th1 cells, but not T regulatory cells. The M1 macrophage show significantly increased CD1d expression compared to M2 macrophage. The ability of NKT cells to suppress myocarditis was shown by adoptive transfer of purified NKT cells into H3-infected NKT knockout (Jα18 knockout) mice, which inhibited cardiac inflammation and increased T regulatory cell response. Cardiac virus titers were equivalent in all mouse strains indicating that neither Vγ4 nor NKT cells participate in control of virus infection. These data show that NKT and Vγ4 cells cross-regulate T regulatory cell responses during CVB3 infections and are the primary factor determining viral pathogenesis in this mouse model.

Mast Cells are Important Modifiers of Autoimmune Disease: With so Much Evidence, Why is There Still Controversy?

There is abundant evidence that mast cells are active participants in events that mediate tissue damage in autoimmune disease. Disease-associated increases in mast cell numbers accompanied by mast cell degranulation and elaboration of numerous mast cell mediators at sites of inflammation are commonly observed in many human autoimmune diseases including multiple sclerosis, rheumatoid arthritis, and bullous pemphigoid. In animal models, treatment with mast cell stabilizing drugs or mast cell ablation can result in diminished disease. A variety of receptors including those engaged by antibody, complement, pathogens, and intrinsic danger signals are implicated in mast cell activation in disease. Similar to their role as first responders in infection settings, mast cells likely orchestrate early recruitment of immune cells, including neutrophils, to the sites of autoimmune destruction. This co-localization promotes cellular crosstalk and activation and results in the amplification of the local inflammatory response thereby promoting and sustaining tissue damage. Despite the evidence, there is still a debate regarding the relative role of mast cells in these processes. However, by definition, mast cells can only act as accessory cells to the self-reactive T and/or antibody driven autoimmune responses. Thus, when evaluating mast cell involvement using existing and somewhat imperfect animal models of disease, their importance is sometimes obscured. However, these potent immune cells are undoubtedly major contributors to autoimmunity and should be considered as important targets for therapeutic disease intervention.

Cross-talk between cd1d-restricted nkt cells and γδ cells in t regulatory cell response

CD1d is a non-classical major histocompatibility class 1-like molecule which primarily presents either microbial or endogenous glycolipid antigens to T cells involved in innate immunity. Natural killer T (NKT) cells and a subpopulation of γδ T cells expressing the Vγ4 T cell receptor (TCR) recognize CD1d. NKT and Vγ4 T cells function in the innate immune response via rapid activation subsequent to infection and secrete large quantities of cytokines that both help control infection and modulate the developing adaptive immune response. T regulatory cells represent one cell population impacted by both NKT and Vγ4 T cells. This review discusses the evidence that NKT cells promote T regulatory cell activation both through direct interaction of NKT cell and dendritic cells and through NKT cell secretion of large amounts of TGFβ, IL-10 and IL-2. Recent studies have shown that CD1d-restricted Vγ4 T cells, in contrast to NKT cells, selectively kill T regulatory cells through a caspase-dependent mechanism. Vγ4 T cell elimination of the T regulatory cell population allows activation of autoimmune CD8+ effector cells leading to severe cardiac injury in a coxsackievirus B3 (CVB3) myocarditis model in mice. CD1d-restricted immunity can therefore lead to either immunosuppression or autoimmunity depending upon the type of innate effector dominating during the infection.

The role of innate immune pathways in type 1 diabetes pathogenesis

PURPOSE OF REVIEW

Type 1 diabetes (T1D) is an autoimmune disease typically believed to result from malfunctions in adaptive immune response signaling which result in activation of self-reactive T cells. However, recent research has indicated components of the innate immune response as having a key role in the initiation of the autoimmune process of T1D. This review will highlight recent studies which examined the role of innate immune response signaling and the connections to T1D pathogenesis.

RECENT FINDINGS

Investigations indicate that components of innate immunity, including inflammation and Toll-like receptor signaling, are involved in pancreatic islet infiltration and insulitis. Recent studies examining the role of viral infections in T1D development also implicate innate immune response signaling in disease pathogenesis.

SUMMARY

Current research indicates that components of innate immune response signaling are involved in the initiation of the autoimmune process which results in the eventual destruction of beta cells during T1D pathogenesis. Continuing efforts by researchers to uncover the molecular pathways of innate immunity linked to T1D development could potentially lead to therapeutics capable of preventing and curing the autoimmune disease.

Reciprocal interactions between human mesenchymal stem cells and gammadelta T cells or invariant natural killer T cells

The immunomodulatory activities of human mesenchymal stem cells (MSCs) provide a rational basis for their application in the treatment of immune-mediated diseases, such as graft versus host disease and multiple sclerosis. The effects of MSCs on invariant natural killer T (iNKT) and gammadelta T cells, both involved in the pathogenesis of autoimmune diseases, are unknown. Here, we investigated the effects of MSCs on in vitro expansion of these unconventional T-cell populations. MSCs inhibited iNKT (Valpha24(+)Vbeta11(+)) and gammadelta T (Vdelta2(+)) cell expansion from peripheral blood mononuclear cells in both cell-to-cell contact and transwell systems. Such inhibition was partially counteracted by indomethacin, a prostaglandin E(2) inhibitor. Block of indoleamine 2,3-deoxygenase and transforming growth factor beta1 did not affect Valpha24(+)Vbeta11(+) and Vdelta2(+) cell expansion. MSCs inhibited interferon-gamma production by activated Valpha24(+)Vbeta11(+) and impaired CD3-mediated proliferation of activated Valpha24(+)Vbeta11(+) and Vdelta2(+) T cells, without affecting their cytotoxic potential. MSCs did not inhibit antigen processing/presentation by activated Vdelta2(+) T cells to CD4(+) T cells. In contrast, MSCs were lysed by activated Vdelta2(+) T cells through a T-cell receptor-dependent mechanism. These results are translationally relevant in view of the increasing interest in MSC-based therapy of autoimmune diseases.

Natural killer cells modulate overt autoimmunity to homeostasis in nonobese diabetic mice after anti-CD3 F(ab')2 antibody treatment through secreting transforming growth factor-beta

Recently, the anti-CD3 antibody has been shown to be a promising candidate for the efficient treatment of overt autoimmunity. However, the mechanisms underlying this effect remain unclear. Our previous studies demonstrated that natural killer (NK)T cells and transforming growth factor (TGF)-beta were key elements in anti-CD3 F(ab')(2)-mediated re-establishment of glucose homeostasis and restoration of self tolerance to islets in type 1 diabetes. In this report, we further investigate the regulatory pathways involved, especially the cellular source of TGF-beta production. The treatment of new-onset nonobese diabetic mice with anti-CD3 F(ab')(2) resulted in a significant increase in the numbers of NK cells in spleen and pancreatic lymph nodes that secrete TGF-beta. Depletion of this cell population with a specific anti-AsGM1 antibody abrogated anti-CD3 F(ab')(2) therapeutic effects and splenic TGF-beta production. When fractionated from recovered mice after CD3 antibody therapy, these NK cells actively suppressed diabetogenic cell proliferation and prevented the cotransfer of diabetes into nonobese diabetic-severe combined immunodeficient mice in a TGF-beta-dependent manner. In addition, the regulatory NKT cells from remitting mice were capable of causing NK cells to exhibit a TGF-beta-producing phenotype by the secretion of the T helper 2 cytokines interleukins 4 and 10. Overall, these data indicate that NK cells are the main source of TGF-beta production after anti-CD3 F(ab')(2) treatment, which are controlled by a population of T helper 2-like NKT cells.

Influence of a non-NK complex region of chromosome 6 on CD4+ invariant NK T cell homeostasis

The number and function of immunoregulatory invariant NKT (iNKT) cells are genetically controlled. A defect of iNKT cell ontogeny and function has been implicated as one causal factor of NOD mouse susceptibility to type 1 diabetes. Other factors of diabetes susceptibility, such as a decrease of regulatory T cell function or an increase in TLR1 expression, are corrected in diabetes-resistant Idd6 NOD.C3H 6.VIII congenic mice. Thus, we surmised that the iNKT cell defects found in NOD mice may also be rescued in congenic mice. Unexpectedly, we found, in both the thymus and the periphery, a 50% reduction in iNKT cell number in NOD.C3H 6.VIII mice as compared with NOD mice. This reduction only affected CD4(+) iNKT cells, and left the double negative iNKT cells unchanged. In parallel, the production of IL-4 and IFN-gamma following alpha-GalCer stimulation was proportionally reduced. Using three subcongenic strains, we have narrowed down the region controlling iNKT development within Idd6 (5.8 Mb) to Idd6.2 region (2.5 Mb). Idd6 region had no effect on NK cell number and in vivo cytotoxic activity. These results indicate that the role of iNKT cells in diabetes development is equivocal and more complex than initially considered. In addition, they bring strong evidence that the regulation of CD4(+) iNKT cell production is independent from that of DN iNKT cells, and involves genes of the Idd6 locus.

Parasites and autoimmunity: the case of fungi

Infectious agents can induce autoimmune diseases in several experimental settings, some of which have clinical counterparts. A variety of mechanisms have been invoked to explain these observations, including molecular mimicry and an increase in the immunogenicity of autoantigens caused by inflammation in the target organ. Paradoxically, infectious agents can also suppress allergic and autoimmune disorders. A central question is to determine whether immune dysregulation precedes, if not promotes, infection or alternatively, but not mutually exclusive, the extent to which microbial exposure/colonization contributes to the burst of pathogenic autoimmunity. Here we discussed recent evidence with fungi that help to accommodate microbes, either commensals or ubiquitous, within the immune homeostasis and its dysregulation.

Extracellular high-mobility group box 1 acts as an innate immune mediator to enhance autoimmune progression and diabetes onset in NOD mice

OBJECTIVE

The implication of innate immunity in type 1 diabetes development has long been proposed. High-mobility group box 1 (HMGB1), an evolutionarily conserved chromosomal protein, was recently recognized to be a potent innate inflammatory mediator when released extracellularly. We sought to test the hypothesis that HMGB1 acts as an innate immune mediator implicated in type 1 diabetes pathogenesis.

RESEARCH DESIGN AND METHODS

Eight- and 12-week-old NOD mice were treated with an HMGB1 neutralizing antibody once a week until 25 weeks of age and monitored for insulitis progression and diabetes onset. The underlying mechanisms of HMGB1 regulation of autoimmune response were further explored.

RESULTS

During autoimmunity, HMGB1 can be passively released from damaged pancreatic beta-cells and actively secreted by islet infiltrated immune cells. Extracellular HMGB1 is potent in inducing NOD dendritic cell maturation and stimulating macrophage activation. Blockade of HMGB1 significantly inhibited insulitis progression and diabetes development in both 8- and 12-week-old NOD mice. HMGB1 antibody treatment decreased the number and maturation of pancreatic lymph node (PLN) CD11c(++)CD11b(+) dendritic cells, a subset of dendritic cells probably associated with autoantigen presentation to naïve T-cells, but increased the number for PLN CD4(+)Foxp3(+) regulatory T-cells. Blockade of HMGB1 also decreased splenic dendritic cell allo-stimulatory capability associated with increased tolergenic CD11c(+)CD8a(+) dendritic cells. Interestingly, the number of CD8(+)interferon-gamma(+) (Tc1) T-cells was increased in the PLNs and spleen after blockade of HMGB1, which could be associated with retarded migration of activated autoreactive T-cells into the pancreatic islets.

CONCLUSIONS

Extracellular HMGB1 functions as a potent innate immune mediator contributing to insulitis progression and diabetes onset.

Resolving the conundrum of islet transplantation by linking metabolic dysregulation, inflammation, and immune regulation

Although type 1 diabetes cannot be prevented or reversed, replacement of insulin production by transplantation of the pancreas or pancreatic islets represents a definitive solution. At present, transplantation can restore euglycemia, but this restoration is short-lived, requires islets from multiple donors, and necessitates lifelong immunosuppression. An emerging paradigm in transplantation and autoimmunity indicates that systemic inflammation contributes to tissue injury while disrupting immune tolerance. We identify multiple barriers to successful islet transplantation, each of which either contributes to the inflammatory state or is augmented by it. To optimize islet transplantation for diabetes reversal, we suggest that targeting these interacting barriers and the accompanying inflammation may represent an improved approach to achieve successful clinical islet transplantation by enhancing islet survival, regeneration or neogenesis potential, and tolerance induction. Overall, we consider the proinflammatory effects of important technical, immunological, and metabolic barriers including: 1) islet isolation and transplantation, including selection of implantation site; 2) recurrent autoimmunity, alloimmune rejection, and unique features of the autoimmune-prone immune system; and 3) the deranged metabolism of the islet transplant recipient. Consideration of these themes reveals that each is interrelated to and exacerbated by the other and that this connection is mediated by a systemic inflammatory state. This inflammatory state may form the central barrier to successful islet transplantation. Overall, there remains substantial promise in islet transplantation with several avenues of ongoing promising research. This review focuses on interactions between the technical, immunological, and metabolic barriers that must be overcome to optimize the success of this important therapeutic approach.

Natural killer cells are required for accelerated type 1 diabetes driven by interferon-beta

The destruction of beta cells by the islet infiltrating lymphocytes causes type 1 diabetes. Transgenic mice models expressing interferon (IFN)-beta in beta cells, in the non-obese diabetic (NOD) strain and in a diabetes-free, major histocompatibility complex-matched, homologous strain, the non-obese resistant (NOR) mice, developed accelerated type 1 diabetes after 3 weeks of age. Our aim was to determine if natural killer (NK) cells could affect the acceleration of the disease. We determined the amount of NK cells in the pancreas, spleen and lymph nodes from NOD rat insulin promoter (RIP)-IFN-beta mice. Pancreatic cytokines were assessed by quantitative real-time polymerase chain reaction and protein arrays. To confirm the relevance of NK cells in the acceleration of autoimmune diabetes this subset was depleted with anti-asialo GM1 antibodies. An increase of intrapancreatic NK cells characterized the accelerated onset of diabetes both in NOD and NOR RIP-IFN-beta transgenic models. Cytokines involved in NK function and migration were found to be hyperexpressed in the pancreas from accelerated diabetic mice. Interestingly, the depletion of NK cells in vivo abolished completely the acceleration of diabetes. NK cells connect innate to adaptive immunity and might play a role in autoimmunity. We report here that NK cells are required critically in the pancreas for accelerated diabetes. This model links inflammation to acceleration of beta cell-specific autoimmunity mediated by NK cells.

Carboxypeptidase D: A Novel TGF-β Target Gene Dysregulated in Patients with Lupus Erythematosus

Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that mainly acts as an inhibitor of immune functions. A lack of functional TGF-beta leads to autoimmune disease in animal models and dysregulated TGF-beta signaling is implicated in human autoimmune diseases. To define target genes that play a part in the inhibitory role of TGF-beta in the immune system, we have identified genes stimulated by TGF-beta in macrophages by gene-chip analysis. One of the TGF-beta regulated genes is carboxypeptidase D (CpD), a 180-kDa type I membrane protein. We have demonstrated that CpD is regulated by TGF-beta in various cell types of both, murine and human origin and, interestingly, is significantly downregulated in CD14 positive cells isolated from patients with lupus erythematosus (LE). Moreover, we show that downregulation of CpD leads to downmodulation of TGF-beta itself, suggesting a role for CpD in a positive feedback loop, providing further evidence for a role of this enzyme in LE. To our knowledge, this is the first report that demonstrates carboxypeptidase D as a TGF-beta target gene that is implicated in the pathogenesis of LE.

The biology of NKT cells

Recognized more than a decade ago, NKT cells differentiate from mainstream thymic precursors through instructive signals emanating during TCR engagement by CD1d-expressing cortical thymocytes. Their semi-invariant alphabeta TCRs recognize isoglobotrihexosylceramide, a mammalian glycosphingolipid, as well as microbial alpha-glycuronylceramides found in the cell wall of Gram-negative, lipopolysaccharide-negative bacteria. This dual recognition of self and microbial ligands underlies innate-like antimicrobial functions mediated by CD40L induction and massive Th1 and Th2 cytokine and chemokine release. Through reciprocal activation of NKT cells and dendritic cells, synthetic NKT ligands constitute promising new vaccine adjuvants. NKT cells also regulate a range of immunopathological conditions, but the mechanisms and the ligands involved remain unknown. NKT cell biology has emerged as a new field of research at the frontier between innate and adaptive immunity, providing a powerful model to study fundamental aspects of the cell and structural biology of glycolipid trafficking, processing, and recognition.

Innate versus Adaptive Immunity: A Paradigm Past Its Prime?

Studies in tumor immunology have relied upon the classic paradigm of distinct innate and adaptive parts of the immune system. However, recent advances in immunology suggest that this division may be overly simplistic, with emerging evidence of a breakdown in conventional hallmarks of each system. Here, we provide an overview of this area and discuss how the concept of a continuum of immune cell populations suggests novel areas of investigation in cancer research.

The heterogeneity of diabetes: unraveling a dispute: is systemic inflammation related to islet autoimmunity?

Diabetes is an emblematic example of a heterogeneous disease. Systemic inflammation has emerged as a prominent factor in the type 2 diabetes pathoetiology, but it remains ill-defined in type 1 diabetes. There is a wide spectrum of associations between inflammatory responses and diabetic syndromes. At one end of this spectrum, there is type 1 diabetes for which there is convincing evidence that chronic inflammation of pancreatic islets is a central aspect of disease pathogenesis. At the opposite end, is type 2 diabetes that is clearly associated with systemic inflammation, which could be either the cause or simply mark the underlying pathology. Accumulating evidence has substantiated that a subgroup of adult patients clinically diagnosed with type 2 diabetes exhibit autoantibody responses to islet autoantigens. The presence of these immunologic abnormalities is associated with a severe insulin secretory defect and the absence of signs of systemic inflammation as documented by plasma C-reactive protein and fibrinogen levels that are comparable with those of control populations. Islet autoantibody evaluation should be part of the diagnostic assessment for clinically diagnosed type 2 diabetes not only because it might predict the rate of progression to insulin requirement in adult populations but also to identify a pathogenically distinct disease phenotype characterized by the absence of systemic inflammation and its related disorders. A more appropriate characterization of this subgroup of clinically diagnosed type 2 diabetes, diabetes of autoimmune pathogenesis, will promote future research into the etiology, natural history, and treatment.

Treatment of new-onset type 1 diabetes with peptide DiaPep277 is safe and associated with preserved beta-cell function: extension of a randomized, double-blind, phase II trial

BACKGROUND

Treatment with DiaPep277, a peptide derived from HSP60, has been shown to preserve beta-cell function in non-obese diabetic mouse (NOD) mice and in a trial with newly diagnosed human patients with type 1 diabetes treated over a 10-month period. This article extends the clinical trial observations to a total of 20 months of treatment to determine the safety and the effects of repeated doses of DiaPep277 on endogenous insulin secretion, metabolic control, and exogenous insulin requirements.

METHODS

Thirty-five male patients (aged 16-58) with a basal C-peptide greater than 0.1 nmol/L were assigned to periodic treatment with DiaPep277 (1 mg) or placebo for a 12-month treatment and 18-month observation protocol, later extended to an additional year of treatment. Stimulated C-peptide, HbA1c, and an exogenous insulin dose were the clinical endpoints.

RESULTS

At 18 months, stimulated C-peptide concentrations had fallen in the placebo group (p = 0.0005) but were maintained in the DiaPep277 group. The need for exogenous insulin was higher in the placebo group than in the DiaPep277 group. Mean HbA1c concentrations were similar in both groups. After extension of the study, patients continuing treatment with DiaPep277 and those switched from placebo to DiaPep277 manifested a trend towards a greater preservation of beta-cell function compared to patients maintained on or switched to placebo. The safety profile of DiaPep277 was similar between the treatment and placebo groups, and no drug-related adverse events occurred.

CONCLUSIONS

Periodic treatment of subjects with DiaPep277 over 2 years was safe and associated preservation of endogenous insulin secretion up to 18 months was observed.

Pivotal roles of CD8+ T cells restricted by MHC class I-like molecules in autoimmune diseases

Unlike T cells restricted by major histocompatibility complex (MHC) class Ia or class II molecules, T cells restricted by MHC class I–like molecules demonstrate properties of both innate and adaptive immunity and are therefore considered innate-like lymphocytes (ILLs). ILLs are believed to have immunoregulatory functions, but their roles in autoimmunity and defense against infections remain elusive. To study the properties of ILLs, we generated mice expressing only MHC class I–like molecules by crossing CIITA^−/− with K^b−/−D^b−/− mice. Surprisingly, these mice developed a lymphoproliferative syndrome and autoimmunity, most notably inflammatory bowel disease (IBD) and insulitis. The CD8⁺ ILLs in these mice exhibit a constitutively activated phenotype, and depletion of these cells abolished the autoimmune disorders. In addition, adoptive transfer of CD8⁺ ILLs from K^b−/−D^b−/−CIITA^−/− mice to Rag-1^−/−pfn^−/− mice also resulted in IBD and insulitis. These findings provide direct evidence that CD8⁺ ILLs are sufficient to initiate and mediate autoimmune diseases.

Evidence of a Functional Role for Mast Cells in the Development of Type 1 Diabetes Mellitus in the BioBreeding Rat

Human type 1 diabetes mellitus (T1DM) arises through autoimmune destruction of pancreatic beta cells and is modeled in many respects by the lymphopenic and spontaneously diabetic BioBreeding (BB) DRlyp/lyp rat. Previously, preonset expression profiling of whole DRlyp/lyp pancreatic lymph nodes (PLN) revealed innate immune activity, specifically that of mast cells and eosinophils. Furthermore, we observed that pancreatic islets of DRlyp/lyp rats as well as those of diabetes-inducible BB DR(+/+) rats potentially recruit innate cells through eotaxin expression. Here we determine that lifelong eotaxin expression begins before 40 days of life and is localized specifically to beta cells. In this report, we find that PLN mast cells are more abundant in DRlyp/lyp compared with related BB DR(+/+) rats (2.1 +/- 0.9% vs 0.9 +/- 0.4% of total cells, p < 0.0001). DRlyp/lyp PLN mast cell gene expression profiling revealed an activated population and included significant overrepresentation of transcripts for mast cell protease 1, cationic trypsinogen, carboxypeptidase A, IL-5, and phospholipase Cgamma. In the DR(+/+) rat, which develops T1DM upon depletion of T regulator cells, mast cells displayed gene expression consistent with the negative regulation of degranulation, including significant overrepresentation of transcripts encoding tyrosine phosphatase SHP-1, lipid phosphatase SHIP, and E3 ubiquitin ligase c-Cbl. To recapitulate the negative mast cell regulation observed in the DR(+/+) rats, we treated DRlyp/lyp rats with the mast cell "stabilizer" cromolyn, which significantly (p < 0.05) delayed T1DM onset. These findings are consistent with a growing body of evidence in human and animal models, where a role for mast cells in the initiation and progression of autoimmune disease is emerging.

The application of microarray analysis to pediatric diseases

DNA microarrays are a tool for simultaneously assessing the expression levels of thousands of genes in a single experiment, making them well-suited to understanding the complex gene response patterns and the regulatory pathways involved in human disease. This article reviews the basics of array technology and analysis, and highlights its application to pediatric diseases.

Human class-I restricted T cell associated molecule is highly expressed in the cerebellum and is a marker for activated NKT and CD8+ T lymphocytes

We have previously reported the characterization of a novel immunoglobulin supergene family member, designated class-I MHC-restricted T cell associated molecule (CRTAM). Here we further characterize human CRTAM and find that it is highly expressed in the cerebellum, notably in Purkinje neurons. We identify CRTAM as a new member of the nectin-like (Necls) family and find significant expression of Necl-2 (IGSF4), a protein known to bind CRTAM and another member of the nectin superfamily, in the cerebellum. These findings suggest that CRTAM/Necl-2 binding may contribute to neuronal interactions. We also show that, in the immune system, CRTAM expression is restricted to activated class-I MHC-restricted T cells, including NKT and CD8 T cells. CRTAM represents one of the most highly expressed surface markers of activated human CD8 T cells and NKT cells, suggesting it may have diagnostic uses in various human viral and autoimmune diseases.

Functional genomics in early autoimmunity

The molecular mechanisms initiating the autoimmune process in type 1 diabetes mellitus (T1DM) remain unknown, and studies aiming to address this question have been compromised by the difficulty of predicting the disease at an early age both in humans and in animal models. An additional hindrance in selecting individuals at an early age has been the complex genetic inheritance of autoimmune diabetes, implicating not only several genes but also environmental factors. We have previously demonstrated the predictive value of insulin autoantibodies (IAAs) at an early age, between three to five weeks in the NOD mouse. Animals positive for early appearance of IAAs (E-IAAs) develop autoimmune diabetes earlier. We showed a correlation between the presence of IAAs in the mothers during pregnancy, E-IAAs in the litters, and the early appearance of T1DM. NOD mice, E-IAA-positive, within litters from IAA-positive mothers during pregnancy, develop diabetes earlier and at a much greater rate than animals that are IAA-negative and from IAA-negative mothers. The molecular mechanisms responsible for this early autoimmune subphenotype were addressed by a global approach to differential gene expression analysis in the pancreatic lymph nodes (PaLNs). Although the data analysis is currently in progress, gene expression signatures were observed that are characteristic for PaLNs with regard to the presence or absence of IAAs. Overall, these data are consistent with the hypothesis of an early environmental influence from the autoimmune maternal environment on the genetic predisposition of the offspring, characterized by specific gene signatures leading to autoimmune disease.