Heterophile antibodies segregate in families and are associated with protection from type 1 diabetes

Anti-serpin antibody-mediated regulation of proteases in autoimmune diabetes

Secretion of anti-serpin B13 autoantibodies in young diabetes-prone nonobese diabetic mice is associated with reduced inflammation in pancreatic islets and a slower progression to autoimmune diabetes. Injection of these mice with a monoclonal antibody (mAb) against serpin B13 also leads to fewer inflammatory cells in the islets and more rapid recovery from recent-onset diabetes. The exact mechanism by which anti-serpin activity is protective remains unclear. We found that serpin B13 is expressed in the exocrine component of the mouse pancreas, including the ductal cells. We also found that anti-serpin B13 mAb blocked the inhibitory activity of serpin B13, thereby allowing partial preservation of the function of its target protease. Consistent with the hypothesis that anti-clade B serpin activity blocks the serpin from binding, exposure to exogenous anti-serpin B13 mAb or endogenous anti-serpin B13 autoantibodies resulted in cleavage of the surface molecules CD4 and CD19 in lymphocytes that accumulated in the pancreatic islets and pancreatic lymph nodes but not in the inguinal lymph nodes. This cleavage was inhibited by an E64 protease inhibitor. Consequently, T cells with the truncated form of CD4 secreted reduced levels of interferon-γ. We conclude that anti-serpin antibodies prevent serpin B13 from neutralizing proteases, thereby impairing leukocyte function and reducing the severity of autoimmune inflammation.

Enhanced anti-serpin antibody activity inhibits autoimmune inflammation in type 1 diabetes

Intracellular (clade B) OVA-serpin protease inhibitors play an important role in tissue homeostasis by protecting cells from death in response to hypo-osmotic stress, heat shock, and other stimuli. It is not known whether these serpins influence immunological tolerance and the risk for autoimmune diseases. We found that a fraction of young autoimmune diabetes-prone NOD mice had elevated levels of autoantibodies against a member of clade B family known as serpinB13. High levels of anti-serpinB13 Abs were accompanied by low levels of anti-insulin autoantibodies, reduced numbers of islet-associated T cells, and delayed onset of diabetes. Exposure to anti-serpinB13 mAb alone also decreased islet inflammation, and coadministration of this reagent and a suboptimal dose of anti-CD3 mAb accelerated recovery from diabetes. In a fashion similar to that discovered in the NOD model, a deficiency in humoral activity against serpinB13 was associated with early onset of human type 1 diabetes. These findings suggest that, in addition to limiting exposure to proteases within the cell, clade B serpins help to maintain homeostasis by inducing protective humoral immunity.

Biochemical analysis of CTLA-4 immunoreactive material from human blood

Background

CTLA-4 was initially described as a membrane-bound molecule that inhibited lymphocyte activation by interacting with B7.1 and B7.2 molecules on antigen presenting cells. Alternative splicing of mRNA encoding the CTLA-4 receptor leads to the production of a molecule (sCTLA-4) that lacks a membrane anchor and is therefore secreted into the extracellular space. Despite studies finding that people with autoimmune disease more frequently express high levels of sCTLA-4 in their blood than apparently healthy people, the significance of these findings is unclear.

Methods

Molecules isolated from blood using CTLA-4 specific antibodies were analyzed with ligand binding assays, mass spectroscopy, and biochemical fractionation in an effort to increase our understanding of CTLA-4 immunoreactive material.

Results

Mass spectroscopy analysis of the molecules recognized by multiple CTLA-4-specific antibodies failed to identify any CTLA-4 protein. Even though these molecules bind to the CTLA-4 receptors B7.1 and B7.2, they also exhibit properties common to immunoglobulins.

Conclusion

We have identified molecules in blood that are recognized by CTLA-4 specific antibodies but also exhibit properties of immunoglobulins. Our data indicates that what has been called sCTLA-4 is not a direct product of the CTLA-4 gene, and that the CTLA-4 protein is not part of this molecule. These results may explain why the relationship of sCTLA-4 to immune system activity has been difficult to elucidate.

Large-scale genetic fine mapping and genotype-phenotype associations implicate polymorphism in the IL2RA region in type 1 diabetes

Genome-wide association studies are now identifying disease-associated chromosome regions. However, even after convincing replication, the localization of the causal variant(s) requires comprehensive resequencing, extensive genotyping and statistical analyses in large sample sets leading to targeted functional studies. Here, we have localized the type 1 diabetes (T1D) association in the interleukin 2 receptor alpha (IL2RA) gene region to two independent groups of SNPs, spanning overlapping regions of 14 and 40 kb, encompassing IL2RA intron 1 and the 5' regions of IL2RA and RBM17 (odds ratio = 2.04, 95% confidence interval = 1.70-2.45; P = 1.92 x 10(-28); control frequency = 0.635). Furthermore, we have associated IL2RA T1D susceptibility genotypes with lower circulating levels of the biomarker, soluble IL-2RA (P = 6.28 x 10(-28)), suggesting that an inherited lower immune responsiveness predisposes to T1D.

Interference in microsphere flow cytometric multiplexed immunoassays for human cytokine estimation

The present study describes positive and negative interference of human cytokine measurement in multiplexed bead-based immunoassays. Significant differences in measured IL-6 and TNF-alpha values in 30 normal human plasma samples were apparent depending on whether measurements were with a 2-plex assay or embedded in a multiplex of 8-or more cytokine antibody pairs, as well as among the kits of 3-different vendors. Sample diluents containing proprietary blocking ingredients were shown to greatly affect the outcome of measured cytokine values. Additionally, recovery of IL-6 and TNF-alpha from spiked samples suggests significant negative interference from either endogenous antibodies, soluble receptors or anti-cytokine antibodies in 10% and 26% of samples, respectively. While it is evident that multiplexed immunoassays hold great promise for cytokine profiling, there are still important issues needing further study. Especially needed are universally optimized sample diluents, uniformly calibrated standards with mass values, and internal assay controls, which should greatly facilitate intralaboratory accuracy and precision and interlaboratory comparisons of cytokine measurements. Possible causes of interference and remedies are discussed.

Autoantibody markers for the diagnosis and prediction of type 1 diabetes

Type 1 diabetes results from the autoimmune destruction of the insulin producing pancreatic beta-cells. For years, the notion that T-lymphocytes played a crucial role in the disorder's formation was considered such sound dogma, that interest in B-lymphocytes and autoantibodies as pathogenic variables was largely relegated to second-class status. However, much of our knowledge regarding the pathogenesis and natural history of this disease has been afforded by analysis of subjects having type 1 diabetes associated autoantibodies. While autoantibodies to more than two dozen autoantigens have been associated with this disease, a majority of interest has been directed at four autoantibodies; islet cell cytoplasmic (ICA), insulin (IAA), glutamic acid decarboxylase (GADA), and IA2/ICA512 autoantigen (IA2A). These autoantibodies, combined with other metabolic and genetic markers, are extremely effective for predicting eventual development of type 1 diabetes in otherwise healthy individuals. These autoantibodies have also aided in our understanding of disease heterogeneity and suggest that the autoimmune processes underlying type 1 diabetes initiate in the earliest stages of life (e.g., initial autoantibody formation at 9-18 months of age). Additional improvements are needed to more accurately define the time to disease onset, response to therapeutic intervention, the pathogenic features of the autoimmune response, and perhaps even the quantity of residual beta cell function.

Functional defects and the influence of age on the frequency of CD4+ CD25+ T-cells in type 1 diabetes

CD4+ CD25+ T-cells appear to play a crucial role in regulating the immune response. Therefore, we evaluated the peripheral blood frequency and function of CD4+ CD25+ T-cells in 70 type 1 diabetic patients and 37 healthy individuals. Interestingly, a positive correlation was observed between increasing age and CD4+ CD25+ T-cell frequency in both subject groups. In contrast to previous studies of nonobese diabetic mice and type 1 diabetic patients, similar frequencies of CD4+ CD25+ and CD4+ CD25(+Bright) T-cells were observed in healthy control subjects and type 1 diabetic patients of similar age. There was no difference between type 1 diabetic subjects of recent-onset versus those with established disease in terms of their CD4+ CD25+ or CD4+ CD25(+Bright) T-cell frequency. However, type 1 diabetic patients were markedly defective in their ability to suppress the proliferation of autologous effector T-cells in vitro. This type 1 diabetes-associated defect in suppression was associated with reduced production of interleukin (IL)-2, gamma-interferon, and transforming growth factor-beta, whereas other cytokines including those of adaptive and innate immunity (IL-10, IL-1beta, IL-6, IL-8, IL-12p70, and tumor necrosis factor-alpha) were similar in control subjects and type 1 diabetic patients. These data suggest that age strongly influences the frequency of CD4+ CD25+ T-cells and that function, rather than frequency, may represent the means by which these cells associate with type 1 diabetes in humans.

Radial artery tonometry demonstrates arterial stiffness in children with type 1 diabetes

OBJECTIVE

To determine if children with type 1 diabetes have increased arterial stiffness by estimating augmentation index with the simple noninvasive technique of radial artery tonometry.

RESEARCH DESIGN AND METHODS

We studied 98 type 1 diabetic children and 57 healthy control subjects, ages 10-18 years, matched for age, sex, race, and BMI, generating 43 matched pairs. Radial artery tonometry was performed, and blood was collected for analysis of fasting lipids, HbA1c, glucose, and cytokines in all children.

RESULTS

Children with diabetes had a significantly higher augmentation index corrected to a heart rate of 75 (AI75) than their matched control subjects. Mean AI75 in type 1 diabetic subjects was 1.11 +/- 10.15 versus -3.32 +/- 10.36 in control subjects. The case-control difference was 5.20 +/- 11.02 (P=0.0031).

CONCLUSIONS

Children with type 1 diabetes have increased arterial stiffness compared with healthy control subjects. Radial artery tonometry is a simple noninvasive technique that could be added to the armamentarium of tests used to provide cardiovascular risk stratification in children with type 1 diabetes.

Adiponectin and leptin concentrations may aid in discriminating disease forms in children and adolescents with type 1 and type 2 diabetes

OBJECTIVE

The incidence of pediatric type 2 diabetes has recently seen an alarming increase. To improve our understanding of pediatric type 2 diabetes and identify markers that discriminate these subjects from those with type 1 diabetes, we performed a multivariant analysis associating serum adiponectin and leptin levels with anthropometrical parameters and disease state.

RESEARCH DESIGN AND METHODS

Samples from children and adolescents with type 1 diabetes (n = 41) and type 2 diabetes (n = 17) and from nondiabetic individuals of similar age from the general population (n = 43) were investigated. An analysis included the parameters of matching for BMI and Tanner stage. Receiver-operator characteristic (ROC) curves were established to assess these analytes' association with disease.

RESULTS

Contrary to studies of adult type 1 diabetes, adiponectin levels in our pediatric type 1 diabetic subjects (10.2 microg/ml [95% CI 8.6-11.7]) did not differ from those of healthy control subjects (10.6 microg/ml [9.2-12.0]; P = NS). Children with type 2 diabetes (5.5 microg/ml [4.8-6.2]) had significantly lower adiponectin levels than both of those groups. Conversely, type 2 diabetic subjects showed marked elevations in serum leptin concentrations (24.3 ng/ml [17.1-31.5]) compared with healthy control subjects (2.7 ng/ml [1.3-4.1]; P < 0.001) and type 1 diabetic subjects (5.1 ng/ml [3.5-6.7]; P < 0.001). Importantly, each of the properties ascribed to pediatric type 2 diabetes was present when the comparison was restricted to healthy children or type 1 diabetic patients whose BMI was >85th percentile or who had Tanner stage 4 and 5. The evaluation of adiponectin-to-leptin ratios revealed a striking difference between children with type 1 diabetes (6.3 [3.8-8.8]) and type 2 diabetes (0.3 [0.2-0.5]; P < 0.001).

CONCLUSIONS

In pediatric diabetes, where diagnosis of disease is often difficult, these studies suggest that the adiponectin-to-leptin ratio may provide additional help in the discrimination between type 1 and type 2 diabetes.

Pro- and anti-inflammatory cytokine production by autoimmune T cells against preproinsulin in HLA-DRB1*04, DQ8 Type 1 diabetes

AIMS/HYPOTHESIS

Preproinsulin is a target T cell autoantigen in human Type 1 diabetes. This study analyses the phenotype and epitope recognition of preproinsulin reactive T cells in subjects with a high genetic risk of diabetes [HLA-DRB1*04, DQ8 with Ab+ (autoantibody-positive) or without islet autoantibodies (control subjects)], and in HLA-matched diabetic patients.

METHODS

A preproinsulin peptide library approach was used to screen for cytokine profiles and epitope specificities in human peripheral blood lymphocytes, and CD4(+)CD45RA(-) and CD4(+)CD45RA(+) T cell subfractions, representing memory and naive and recently primed T cells respectively.

RESULTS

In CD4(+) T cell subsets we identified immunodominant epitopes and cytokine production patterns that differed profoundly between patients, Ab+ subjects and non-diabetic HLA-matched control subjects. In Ab+ subjects, a C-peptide epitope C13-29 and insulin B-chain epitope B11-27 were preferentially recognised, whereas insulin-treated Type 1 diabetic patients reacted to native insulin and B-chain epitope B1-16. In peripheral blood lymphocytes of Ab+ subjects, an increase in T helper (Th) 1 (IFNgamma, IL-2) and Th2 (IL-4) cytokines was detectable, wheras in CD45RA(+) and CD45RA(-) subsets, IL-4 and IL-10 phenotypes dominated, compatible with the contribution of non-CD4 cells to IFNgamma content. In insulin-treated Type 1 diabetic patients, naive and recently primed CD4(+) cells were characterised by increasd IFNgamma, TNFalpha, and IL-5.

CONCLUSIONS/INTERPRETATION

Our data show that T cell reactivity to preproinsulin in CD45RA subsets is Th2-dominant in Ab+ subjects, challenging the Th1 paradigm in Type 1 diabetes. Characteristic immunodominant epitopes and cytokine patterns distinguish diabetic patients and Ab+ subjects from HLA-matched healthy individuals. This could prove useful in monitoring of T-cell immunity in clinical diabetes intervention trials.

An association of autoantibody status and serum cytokine levels in type 1 diabetes

At onset of type 1 diabetes, the islet autoantibody status of patients has been reported to predict progression of the disease. We therefore tested the hypothesis that the systemic immunoregulatory balance, as defined by levels of circulating cytokines and chemokines, is associated with islet autoantibody status. In 50 patients with recent-onset type 1 diabetes, antibodies to GAD and insulinoma-associated antigen 2 (IA-2) were analyzed by radioimmunoassay; cytoplasmic islet cell antibodies were determined by indirect immunofluorescence. Cytokine and chemokine concentrations were measured by rigidly evaluated double antibody enzyme-linked immunosorbent assay. Of four classically defined Th1/Th2 cytokines (gamma-interferon, interleukin [IL]-5, IL-10, IL-13), none showed an association with multiple autoantibody positivity. Of six mediators mainly produced by innate immunity cells, three were associated with multiple autoantibody status (IL-18 increased, MIF and MCP-1 decreased) and three were unaffected (IL-12, MIP-1beta, IP-10). GAD and/or IA-2 antibody titers negatively correlated with systemic concentrations of MIF, MIP-1beta, and IL-12. Combining the data of several cytokine and chemokine levels made it possible to predict islet antibody positivity in individual patients with 85% sensitivity and 94% specificity. These data suggest a close association of islet antibody status with systemic immunoregulation in type 1 diabetes.

Cytokine detection by ELISPOT: relevance for immunological studies in type 1 diabetes

Diabetes mellitus type 1 is a chronic disease in which the insulin-secreting ss-cells are selectively destroyed by an immune-mediated process. Autoantibodies directed against several islet antigens are useful parameters to estimate the risk to develop diabetes, but cell-mediated immunity involving T lymphocytes plays a major part in causing the specific destruction of ss-cells. T cells are characterized by their antigen-specificity, phenotype and cytokine-secreting profile. T cells that secrete cytokines of the T helper 1 (Th1) type have been shown to transfer diabetes in animal studies, in contrast to T helper 2 (Th2) cytokine-secreting T cells that are thought to be rather nondestructive. In the absence of phenotypic markers for Th1 and Th2 cells, several different approaches have been taken to examine T cell responses in detail. Methods involve T-cell proliferation assays, Enzyme-Linked-Immuno-Sorbent-Assay (ELISA) analysis of secreted cytokines and phenotype analysis applying flow cytometry. A more recent development is ELISPOT analysis, which enables the investigator to determine the qualitative and quantitative antigen-specific immune response on a single-cell level with regard to cytokine secretion. This article aims to give an introduction to the advantages and limitations inherent in the different techniques and their potential relevance for immunological studies in diabetes mellitus type 1.

Heterophile antibodies indicate progression of autoimmunity in human type 1 diabetes mellitus before clinical onset

We previously reported serum cytokines in a group of long term non-progressors to Type 1 diabetes; this reactivity detected in ELISA is now identified as heterophile antibody in some sera. Here, we characterize heterophile antibody activity. A 14 kDa-polypeptide from heterophile antibody containing serum bound to an anti-IL-4 column, but IL-4 was not detected by Western blot or by MS/MS sequencing. However, in 2/13 heterophile antibody positive sera, T-cell growth was potentiated and was blocked by an anti-human immunoglobulin. To examine the relationship between low affinity heterophile antibody presence and disease progression, 1100 archived serum samples were analyzed with two pairs of antibodies from 443 diabetes-free first degree relatives of Type 1 diabetes mellitus patients for heterophile antibody; 95 individuals developed diabetes on follow-up. Twenty-two individuals, whose serum was heterophile antibody positive with the second pair of antibodies (but negative with the first pair of antibodies), had a significantly higher incidence of developing diabetes after five years. Thirty-seven individuals with heterophile antibody reactivity with the first pair of antibodies, regardless of reactivity with the second pair of antibodies, had a significantly lower incidence of developing diabetes. While we cannot exclude the presence of genuine cytokine in all sera, these data indicate the presence of distinct groups of heterophile antibodies in patients at high risk to develop diabetes. Thus, anti-Ig heterophilic antibodies with different immunochemical reactivities are linked to the progression of or protection from Type 1 diabetes autoimmunity.

Serum IFN-gamma and IL-10 levels are associated with disease progression in non-obese diabetic mice

BACKGROUND

The goal of the present study was to determine whether cytokines in the peripheral blood of naive NOD mice correlate with the disease process and thereby would provide a marker for monitoring disease activity.

METHODS

Female NOD mice (5, 10 and 14-16 weeks of age) were investigated in a cross-sectional study. In the group of 14-16-week-old mice, non-diabetic and diabetic mice were analysed as different subgroups. The Th1 cytokine (IFN-gamma) and the Th2 cytokine (IL-10) were quantified in serum by sandwich enzyme-linked immunosorbent assay (ELISA). Pancreatic mRNA for IFN-gamma and IL-10 was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) from the same animals.

RESULTS

Serum levels of IFN-gamma were initially low but increased with age in NOD mice, reaching the highest levels at diabetes onset (p<0.002 compared to 10 weeks). A similar rise was noted in IFN-gamma gene expression in pancreatic lesions. In contrast, an early peak of serum IL-10 levels was observed in non-diabetic NOD mice (10 weeks) at a stage where non-destructive insulitis occurs. With increasing age a continuous loss of IL-10 until progression towards diabetes was observed. The pancreatic IL-10 mRNA expression correlated with serum IL-10 changes. As a consequence, the ratio of IFN-gamma/IL-10, reflecting the Th1/Th2 balance in the serum, was significantly increased in diabetic compared to non-diabetic NOD mice (p<0.005).

CONCLUSION

These results demonstrate, for the first time, that an increased Th2 pattern in the non-diabetic stage preceding a Th1 shift is associated with the development of diabetes in naive NOD mice. Serum cytokines correlate with disease progression and pancreatic cytokine expression during prediabetes. Soluble cytokines measured in the periphery are therefore promising surrogate markers of diabetes development.

Adeno-associated virus vector-mediated IL-10 gene delivery prevents type 1 diabetes in NOD mice

The development of spontaneous autoimmune diabetes in nonobese diabetic (NOD) mice provides for their use as a model of human type 1 diabetes. To test the feasibility of muscle-directed gene therapy to prevent type 1 diabetes, we developed recombinant adeno-associated virus (rAAV) vectors containing murine cDNAs for immunomodulatory cytokines IL-4 or IL-10. Skeletal muscle transduction of female NOD mice with IL-10, but not IL-4, completely abrogated diabetes. rAAV-IL-10 transduction attenuated the production of insulin autoantibodies, quantitatively reduced pancreatic insulitis, maintained islet insulin content, and altered splenocyte cytokine responses to mitogenic stimulation. The beneficial effects were host specific, as adoptive transfer of splenocytes from rAAV IL-10-treated animals rapidly imparted diabetes in naive hosts, and the cells contained no protective immunomodulatory capacity, as defined through adoptive cotransfer analyses. These results indicate the utility for rAAV, a vector with advantages for therapeutic gene delivery, to transfer immunoregulatory cytokines capable of preventing type 1 diabetes. In addition, these studies provide foundational support for the concept of using immunoregulatory agents delivered by rAAV to modulate a variety of disorders associated with deleterious immune responses, including allergic reactions, transplantation rejection, immunodeficiencies, and autoimmune disorders.

Clinical application of NKT cell assays to the prediction of type 1 diabetes

Type 1 diabetes is a disease characterised by disturbed glucose homeostasis, which results from autoimmune destruction of the insulin-producing beta cells in the pancreas. The autoimmune attack, while not yet fully characterised, exhibits components of both mis-targeting and failed tolerance induction. The involvement of non-classical lymphocytes in the induction and maintenance of peripheral tolerance has recently been recognised and natural killer T (NKT) cells appear to play such a role. NKT cells are a subset of T cells that are distinct in being able to produce cytokines such as IL-4 and IFN-gamma extremely rapidly following activation. These lymphocytes also express some surface receptors, and the lytic activity, characteristic of NK cells. Deficiencies in NKT cells have been identified in animal models of type 1 diabetes, and a causal association has been demonstrated by adoptive transfer experiments in diabetes-prone NOD mice. Preliminary work suggests that a similar relationship may exist between deficiencies in NKT cells and type 1 diabetes in humans, although the techniques reported to date would be difficult to translate to clinical use. Here, we describe methods appropriate to the clinical assessment of NKT cells and discuss the steps required in the assessment and validation of NKT cell assays as a predictor of type 1 diabetes.

False Positivity in a Cyto-ELISA for Anti-Endothelial Cell Antibodies Caused by Heterophile Antibodies to Bovine Serum Proteins

Background: ELISAs with fixed endothelial cells or cell lines are widely used screening tests for anti-endothelial cell antibodies (AECAs), but spurious increases occur. We examined interferences by heteroantibodies and means to eliminate them.

Methods: AECAs were measured by ELISA on fixed layers of the human endothelial cell line, EA.hy 926, in a panel of 60 patient serum samples diluted in bovine serum albumin. Heteroantibodies against fetal calf serum (FCS) proteins were demonstrated and characterized in an ELISA—the interference assay—that used FCS-coated plates and Tween 20-containing buffer as blocking agent and sample diluent, as well as by immunoblotting.

Results: In 12 of 60 patient serum samples, spurious increases of AECA titers were produced by endogenous antibodies reacting with FCS proteins from culture medium that were coated onto the solid-phase at the time of cell plating. This mechanism of interference was supported experimentally by exposing extracellular matrix, varying cell density, and incubating wells with FCS alone. The heterophile antibodies were mainly IgG and IgA, and in inhibition experiments, they recognized serum proteins from goat, sheep, and horse. Washing cells free of FCS before plating, or adding FCS (100 mL/L) to the patient sample diluent eliminated spurious signals from all 30 tested sera, but the latter method had practical advantages.

Conclusions: Antibodies against animal serum proteins are a frequent cause of erroneous results in cyto-ELISAs. The interference can be eliminated by simple antibody absorption in FCS-containing dilution buffer.