Autoantibodies to the islet antigen ICA69 occur in IDDM and in rheumatoid arthritis

ICA1 affects APP processing through the PICK1-PKCα signaling pathway

AIMS

Islet cell autoantigen 1 (ICA1) is involved in autoimmune diseases and may affect synaptic plasticity as a neurotransmitter. Databases related to Alzheimer's disease (AD) have shown decreased ICA1 expression in patients with AD. However, the role of ICA1 in AD remains unclear. Here, we report that ICA1 expression is decreased in the brains of patients with AD and an AD mouse model.

RESULTS

The ICA1 increased the expression of amyloid precursor protein (APP), disintegrin and metalloprotease 10 (ADAM10), and disintegrin and metalloprotease 17 (ADAM17), but did not affect protein half-life or mRNA levels. Transcriptome sequencing analysis showed that ICA1 regulates the G protein-coupled receptor signaling pathway. The overexpression of ICA1 increased PKCα protein levels and phosphorylation.

CONCLUSION

Our results demonstrated that ICA1 shifts APP processing to non-amyloid pathways by regulating the PICK1-PKCα signaling pathway. Thus, this study suggests that ICA1 is a novel target for the treatment of AD.

Differentially methylated and expressed genes in familial type 1 diabetes

There has recently been a growing interest in examining the role of epigenetic modifications, such as DNA methylation, in the etiology of type 1 diabetes (T1D). This study aimed to delineate differences in methylation patterns between T1D-affected and healthy individuals by examining the genome-wide methylation of individuals from three Arab families from Kuwait with T1D-affected mono-/dizygotic twins and non-twinned siblings. Bisulfite sequencing of DNA from the peripheral blood of the affected and healthy individuals from each of the three families was performed. Methylation profiles of the affected individuals were compared to those of the healthy individuals Principal component analysis on the observed methylation profiling based on base-pair resolution clustered the T1D-affected twins together family-wide. The sites/regions that were differentially methylated between the T1D and healthy samples harbored 84 genes, of which 18 were known to be differentially methylated in T1D individuals compared to healthy individuals in publicly available gene expression data resources. We further validated two of the 18 genes—namely ICA1 and DRAM1 that were hypermethylated in T1D samples compared to healthy samples—for upregulation in T1D samples from an extended study cohort of familial T1D. The study confirmed that the ICA1 and DRAM1 genes are differentially expressed in T1D samples compared to healthy samples.

Islet-cell autoantigen 69 mediates the antihyperalgesic effects of electroacupuncture on inflammatory pain by regulating spinal glutamate receptor subunit 2 phosphorylation through protein interacting with C-kinase 1 in mice

Supplemental Digital Content is Available in the Text.

A clear role of ICA69 in mediating the antihyperalgesic effects of electroacupuncture was confirmed, and the ICA69-PICK1-GluR2 molecular mechanism to explain these effects is proposed.

Electroacupuncture (EA) is widely used in clinical settings to reduce inflammatory pain. Islet-cell autoantigen 69 (ICA69) has been reported to regulate long-lasting hyperalgesia in mice. ICA69 knockout led to reduced protein interacting with C-kinase 1 (PICK1) expression and increased glutamate receptor subunit 2 (GluR2) phosphorylation at Ser880 in spinal dorsal horn. In this study, we evaluated the role of ICA69 in the antihyperalgesic effects of EA and the underlying mechanism through regulation of GluR2 and PICK1 in spinal dorsal horn. Hyperalgesia was induced in mice with subcutaneous plantar injection of complete Freund adjuvant (CFA) to cause inflammatory pain. Electroacupuncture was then applied for 30 minutes every other day after CFA injection. When compared with CFA group, paw withdrawal frequency of CFA+EA group was significantly decreased. Remarkable increases in Ica1 mRNA expression and ICA69 protein levels on the ipsilateral side were detected in the CFA+EA group. ICA69 expression reached the peak value around day 3. More importantly, ICA69 deletion impaired the antihyperalgesic effects of EA on GluR2-p, but PICK1 deletion could not. Injecting ICA69 peptide into the intrathecal space of ICA69-knockout mice mimicked the effects of EA analgesic and inhibited GluR2-p. Electroacupuncture had no effects on the total protein of PICK1 and GluR2. And, EA could increase the formation of ICA69-PICK1 complexes and decrease the amount of PICK1-GluR2 complexes. Our findings indicate that ICA69 mediates the antihyperalgesic effects of EA on CFA-induced inflammatory pain by regulating spinal GluR2 through PICK1 in mice.

Structure and function of the exocrine pancreas in patients with type 1 diabetes

In the last 10 years, several studies have shown that the pancreas of patients with type 1 diabetes (T1D), and even of subjects at risk for T1D, was smaller than the pancreas from healthy subjects. This arose the question of the relationships between the endocrine and exocrine parts of the pancreas in T1D pathogenesis. Our review underlines that histological anomalies of the exocrine pancreas are common in patients with T1D: intralobular and interacinar fibrosis, acinar atrophy, fatty infiltration, leucocytic infiltration, and pancreatic arteriosclerosis are all frequent observations. Moreover, 25% to 75% of adult patients with T1D present with pancreatic exocrine dysfunction. Our review summarizes the putative causal factors for these structural and functional anomalies, including: 1/ alterations of insulin, glucagon, somatostatin and pancreatic polypeptide secretion, 2/ global pancreatic inflammation 3/ autoimmunity targeting the exocrine pancreas, 4/ vascular and neural abnormalities, and 5/ the putative involvement of pancreatic stellate cells. These observations have also given rise to new theories on T1D: the primary event of T1D pathogenesis could be non-specific, e.g bacterial or viral or chemical, resulting in global pancreatic inflammation, which in turn could cause beta-cell predominant destruction by the immune system. Finally, this review emphasizes that it is advisable to evaluate pancreatic exocrine function in patients with T1D presenting with gastro-intestinal complaints, as a clinical trial has shown that pancreatic enzymes replacement therapy can reduce the frequency of hypoglycemia and thus might improve quality of life in subjects with T1D and exocrine failure.

Expression-Based Genome-Wide Association Study Links Vitamin D-Binding Protein With Autoantigenicity in Type 1 Diabetes

Type 1 diabetes (T1D) is caused by autoreactive T cells that recognize pancreatic islet antigens and destroy insulin-producing β-cells. This attack results from a breakdown in tolerance for self-antigens, which is controlled by ectopic antigen expression in the thymus and pancreatic lymph nodes (PLNs). The autoantigens known to be involved include a set of islet proteins, such as insulin, GAD65, IA-2, and ZnT8. In an attempt to identify additional antigenic proteins, we performed an expression-based genome-wide association study using microarray data from 118 arrays of the thymus and PLNs of T1D mice. We ranked all 16,089 protein-coding genes by the likelihood of finding repeated differential expression and the degree of tissue specificity for pancreatic islets. The top autoantigen candidate was vitamin D-binding protein (VDBP). T-cell proliferation assays showed stronger T-cell reactivity to VDBP compared with control stimulations. Higher levels and frequencies of serum anti-VDBP autoantibodies (VDBP-Abs) were identified in patients with T1D (n = 331) than in healthy control subjects (n = 77). Serum vitamin D levels were negatively correlated with VDBP-Ab levels in patients in whom T1D developed during the winter. Immunohistochemical localization revealed that VDBP was specifically expressed in α-cells of pancreatic islets. We propose that VDBP could be an autoantigen in T1D.

Discover hidden splicing variations by mapping personal transcriptomes to personal genomes

RNA-seq has become a popular technology for studying genetic variation of pre-mRNA alternative splicing. Commonly used RNA-seq aligners rely on the consensus splice site dinucleotide motifs to map reads across splice junctions. Consequently, genomic variants that create novel splice site dinucleotides may produce splice junction RNA-seq reads that cannot be mapped to the reference genome. We developed and evaluated an approach to identify ‘hidden’ splicing variations in personal transcriptomes, by mapping personal RNA-seq data to personal genomes. Computational analysis and experimental validation indicate that this approach identifies personal specific splice junctions at a low false positive rate. Applying this approach to an RNA-seq data set of 75 individuals, we identified 506 personal specific splice junctions, among which 437 were novel splice junctions not documented in current human transcript annotations. 94 splice junctions had splice site SNPs associated with GWAS signals of human traits and diseases. These involve genes whose splicing variations have been implicated in diseases (such as OAS1), as well as novel associations between alternative splicing and diseases (such as ICA1). Collectively, our work demonstrates that the personal genome approach to RNA-seq read alignment enables the discovery of a large but previously unknown catalog of splicing variations in human populations.

Human fibrocytes express multiple antigens associated with autoimmune endocrine diseases

CONTEXT

Factors common to multiple autoimmune diseases have been sought vigorously. Graves' disease (GD) and type 1 diabetes mellitus (T1DM) involve end-organ remodeling. Fibrocytes participate in inflammatory diseases and were recently shown to express thyroid-specific proteins such as the thyrotropin receptor and thyroglobulin.

OBJECTIVE

The objective of the study was to determine whether a broader repertoire of autoantigen expression, such as proteins associated with T1DM, can be ascribed to fibrocytes.

DESIGN, SETTING, AND PARTICIPANTS

Fibrocytes and fibroblasts were collected and analyzed from healthy individuals and those with autoimmune diseases in an academic clinical practice.

MAIN OUTCOME MEASURES

Real-time PCR, Western blot analysis, gene promoter analysis, cell transfections, and flow cytometric cell sorting were performed.

RESULTS

Islet cell antigen ICA512 (IA-2) and islet cell autoantigen of 69 kDa (ICA69), two islet-specific proteins implicated in T1DM, are expressed by fibrocytes from healthy donors and those with T1DM, GD, and multiple sclerosis. Both transcripts are detected by PCR, the proteins are resolved on Western blots, and both gene promoters are active in fibrocytes. Levels of ICA69 are substantially higher than those of IA-2 in fibrocytes. ICA69 localizes to CD34(+) GD orbital fibroblasts putatively derived from fibrocytes, whereas higher levels of IA-2 are found in CD34(-) fibroblasts.

CONCLUSIONS

In addition to autoantigens implicated in thyroid autoimmunity, fibrocytes and derivative fibroblasts express multiple autoantigens associated with T1DM. This expression results from active gene promoters and abundant steady-state mRNA encoding ICA69 and IA-2. These latest findings demonstrate that fibrocytes express antigens relevant to multiple forms of endocrine autoimmunity. They suggest the potential for these cells playing a direct role in immune reactivity directed at the thyroid and pancreatic islets.

Antigen targets of type 1 diabetes autoimmunity

Type 1 diabetes is characterized by recognition of one or more β-cell proteins by the immune system. The list of target antigens in this disease is ever increasing and it is conceivable that additional islet autoantigens, possibly including pivotal β-cell targets, remain to be discovered. Many knowledge gaps remain with respect to the disorder's pathogenesis, including the cause of loss of tolerance to islet autoantigens and an explanation as to why targeting of proteins with a distribution of expression beyond β cells may result in selective β-cell destruction and type 1 diabetes. Yet, our knowledge of β-cell autoantigens has already led to translation into tissue-specific immune intervention strategies that are currently being assessed in clinical trials for their efficacy to halt or delay disease progression to type 1 diabetes, as well as to reverse type 1 diabetes. Here we will discuss recently gained insights into the identity, biology, structure, and presentation of islet antigens in relation to disease heterogeneity and β-cell destruction.

Immunobiology of beta-cell destruction

Type 1 diabetes is a chronic disease characterized by severe insulin deficiency and hyperglycemia, due to autoimmune destruction of pancreatic islets of Langerhans. A susceptible genetic background is necessary, but not sufficient, for the development of the disease. Epidemiological and clinical observations underscore the importance of environmental factors as triggers of type 1 diabetes, currently under investigation. Islet-specific autoantibodies precede clinical onset by months to years and are established tools for risk prediction, yet minor players in the pathogenesis of the disease. Many efforts have been made to elucidate disease-relevant defects in the key immune effectors of islet destruction, from the early failure of specific tolerance to the vicious circle of destructive insulitis. However, the events triggering islet autoimmunity as well as the transition to overt diabetes are still largely unknown, making prevention and treatment strategies still a challenge.

Islet autoantigens: structure, function, localization, and regulation

Islet autoantigens associated with autoimmune type 1 diabetes (T1D) are expressed in pancreatic β cells, although many show wider patterns of expression in the neuroendocrine system. Within pancreatic β cells, every T1D autoantigen is in one way or another linked to the secretory pathway. Together, these autoantigens play diverse roles in glucose regulation, metabolism of biogenic amines, as well as the regulation, formation, and packaging of secretory granules. The mechanism(s) by which immune tolerance to islet-cell antigens is lost during the development of T1D, remains unclear. Antigenic peptide creation for immune presentation may potentially link to the secretory biology of β cells in a number of ways, including proteasomal digestion of misfolded products, exocytosis and endocytosis of cell-surface products, or antigen release from dying β cells during normal or pathological turnover. In this context, we evaluate the biochemical nature and immunogenicity of the major autoantigens in T1D including (pro)insulin, GAD65, ZnT8, IA2, and ICA69.

Sequence variation in promoter of Ica1 gene, which encodes protein implicated in type 1 diabetes, causes transcription factor autoimmune regulator (AIRE) to increase its binding and down-regulate expression

ICA69 (islet cell autoantigen 69 kDa) is a protein implicated in type 1 diabetes mellitus in both the non-obese diabetic (NOD) mouse model and humans. ICA69 is encoded by the Ica1 gene on mouse chromosome 6 A1-A2. We previously reported reduced ICA69 expression in the thymus of NOD mice compared with thymus of several non-diabetic mouse strains. We propose that reduced thymic ICA69 expression could result from variations in transcriptional regulation of the gene and that polymorphisms within the Ica1 core promoter may partially determine this transcriptional variability. We characterized the functional promoter of Ica1 in NOD mice and compared it with the corresponding portions of Ica1 in non-diabetic C57BL/6 mice. Luciferase reporter constructs demonstrated that the NOD Ica1 promoter region exhibited markedly reduced luciferase expression in transiently transfected medullary thymus epithelial (mTEC(+)) and B-cell (M12)-derived cell lines. However, in a non-diabetic strain, C57BL/6, the Ica1 promoter region was transcriptionally active when transiently transfected into the same cell lines. We concomitantly identified five single nucleotide polymorphisms within the NOD Ica1 promoter. One of these single nucleotide polymorphisms increases the binding affinity for the transcription factor AIRE (autoimmune regulator), which is highly expressed in thymic epithelial cells, where it is known to play a key role regulating self-antigen expression. We conclude that polymorphisms within the NOD Ica1 core promoter may determine AIRE-mediated down-regulation of ICA69 expression in medullary thymic epithelial cells, thus providing a novel mechanistic explanation for the loss of immunologic tolerance to this self-antigen in autoimmunity.

Identification of a common autoantigenic epitope of protein disulfide isomerase, golgin-160 and voltage-gated potassium channel in type 1 diabetes

A common epitope of proteins golgin-160, voltage-gated potassium channel and disulfide isomerase was identified by screening with autoantibodies of a type 1 diabetic (T1D) patient a lambdaUni-Zap cDNA library from human diabetic islets. The significance of the identified autoantigens to the disease pathogenesis remains to be elucidated.

Immunology of beta-cell destruction

The pancreatic islet beta-cells are the target for an autoimmune process that eventually results in an inability to control blood glucose due to the lack of insulin. The different steps that eventually lead to the complete loss of the beta-cells are reviewed to include the very first step of a triggering event that initiates the development of beta-cell autoimmunity to the last step of appearance of islet-cell autoantibodies, which may mark that insulitis is about to form. The observations that the initial beta-cell destruction by virus or other environmental factors triggers islet autoimmunity not in the islets but in the draining pancreatic lymph nodes are reviewed along with possible basic mechanisms of loss of tolerance to islet autoantigens. Once islet autoimmunity is established the question is how beta-cells are progressively killed by autoreactive lymphocytes which eventually results in chronic insulitis. Many of these series of events have been dissected in spontaneously diabetic mice or rats, but controlled clinical trials have shown that rodent observations are not always translated into mechanisms in humans. Attempts are therefore needed to clarify the step 1 triggering mechanisms and the step to chronic autoimmune insulitis to develop evidence-based treatment approaches to prevent type 1 diabetes.

Metabolic and genomic dissection of diabetes in the Cohen rat

We investigated the metabolic and genetic basis of diabetes in the Cohen Diabetic rat, a model of diet-induced diabetes, as a means to identify the molecular mechanisms involved. By altering individual components in the diabetogenic diet, we established that the dietary susceptibility that leads to the development of diabetes in this model is directly related to the high casein and low copper content in chow. The development of diabetes is accompanied by depletion of the acini from the exocrine pancreas and replacement with fat cells, while the appearance of the islets of Langerhans remains intact. With reversion back from diabetogenic to regular diet, the diabetic phenotype disappears but the histological changes in the exocrine pancreas prevail. Using positional cloning, we detected a major quantitative trait locus (QTL) on rat chromosome 4 with a chromosomal span of 4.9 cM, and two additional loci on chromosomes 7 and X. A screen for genes within that QTL in the rat and in the syntenic regions in mouse and man revealed only 23 candidate genes. Notable among these genes is Ica1, which has been causally associated with diabetes and bovine casein. We conclude that the development of diabetes in our model is dependent upon high casein and low copper in diet, that it is accompanied by histomorphological changes in the exocrine but not endocrine pancreas, that it is reversible, and that it is associated with a major QTL on chromosome 4 in which we detected Ica1, a high priority candidate gene.

Importin beta: a novel autoantigen in human autoimmunity identified by screening random peptide libraries on phage

By screening random peptide libraries (RPLs) with sera of Type 1 diabetes (T1D) patients, we previously identified 5 disease-specific 'mimotopes' displayed on phages (phagotopes). We already characterised 1 phagotope (CH1p), as an epitope of human osteopontin, an autoantigen expressed within the somatostatin cells of human islets. In this paper, we report the characterization of the second phagotope, 195Dyn, by immunohistochemistry, Western Blotting and screening of a human islet cDNA library using rabbit anti-195Dyn antibodies. The 195Dyn mimotope was detected in human islets. The screening of a lambdagt11 cDNA library from human islets has identified a clone, which corresponded to human importin beta. ELISA detected autoantibodies against this protein in sera of around 60% of TD1 patients and in 30% of patients affected by other autoimmune diseases. In summary, RPLs technology proved again successful in identifying another novel autoantigen (importin beta), whose significance in the autoimmune process remains to be fully elucidated.

Anti-CD38 autoimmunity in children with newly diagnosed type 1 diabetes mellitus

AIMS

To test for anti-CD38 autoimmunity in children with newly-diagnosed type 1 diabetes mellitus (DM1).

METHODS

Serum anti-CD38 autoantibodies were detected by Western blot in 270 children (130 girls, 140 boys, mean age 8 +/- 4 years) with newly-diagnosed DM1 and 179 gender- and age-matched non-diabetic children. In 126 diabetic children, another blood sample was obtained 15 +/- 4 months after the diagnosis.

RESULTS

Anti-CD38 autoantibody titers at least 3 SD above the mean value for the control group were found in 4.4% of children with DM1 vs 0.6% of controls (chi2 = 5.8, p <0.016). No statistical differences were observed between anti-CD38 positive and negative patients in terms of phenotype. At follow-up, of six diabetic children who were positive for anti-CD38 antibodies, two were new cases. A positive correlation was found between the antibody titer of diabetic sera at diagnosis and follow up (r = 0.46, p <0.0001).

CONCLUSION

An autoimmune reaction against CD38, a protein expressed in human islets, is associated with newly-diagnosed DM1. In children with DM1, CD38 autoimmunity increases with time and persists.

Developments in the prediction of type 1 diabetes mellitus, with special reference to insulin autoantibodies

The prodromal phase of type 1 diabetes is characterised by the appearance of multiple islet-cell related autoantibodies (Aab). The major target antigens are islet-cell antigen, glutamic acid decarboxylase (GAD), protein-tyrosine phosphatase-2 (IA-2) and insulin. Insulin autoantibodies (IAA), in contrast to the other autoimmune markers, are the only beta-cell specific antibodies. There is general consensus that the presence of multiple Aab (> or = 3) is associated with a high risk of developing diabetes, where the presence of a single islet-cell-related Aab has usually a low predictive value. The most commonly used assay format for the detection of Aab to GAD, IA-2 and insulin is the fluid-phase radiobinding assay. The RBA does not identify or measure Aab, but merely detects its presence. However, on the basis of molecular studies, disease-specific constructs of GAD and IA-2 have been employed leading to somewhat improved sensitivity and specificity of the RBA. Serological studies have shown epitope restriction of IAA that can differentiate diabetes-related from unrelated IAA, but current assays do not distinguish between disease-predictive and non-predictive IAA or between IAA and insulin antibodies (IA). More recently, phage display technology has been successful in identifying disease-specific anti-idiotopes of insulin. In addition, phage display has facilitated the in vitro production of antibodies with high affinity. Identification of disease-specific anti-idiotopes of insulin should enable the production of a high affinity reagent against the same anti-idiotope. Such a development would form the basis of a disease-specific radioimmunoassay able to identify and measure particular idiotypes, rather than merely detect and titrate IAA.

Alternative core promoters regulate tissue-specific transcription from the autoimmune diabetes-related ICA1 (ICA69) gene locus

Islet cell autoantigen 69-kDa (ICA69), protein product of the human ICA1 gene, is one target of the immune processes defining the pathogenesis of Type 1 diabetes. We have characterized the genomic structure and functional promoters within the 5'-regulatory region of ICA1. 5'-RNA ligase-mediated rapid amplification of cDNA ends evaluation of ICA1 transcripts expressed in human islets, testis, heart, and cultured neuroblastoma cells reveals that three 5'-untranslated region exons are variably expressed from the ICA1 gene in a tissue-specific manner. Surrounding the transcription initiation sites are motifs characteristic of non-TATA, non-CAAT, GC-rich promoters, including consensus Sp1/GC boxes, an initiator element, cAMP-responsive element-binding protein (CREB) sites, and clusters of other putative transcription factor sites within a genomic CpG island. Luciferase reporter constructs demonstrate that the first two ICA1 exon promoters reciprocally stimulate luciferase expression within islet- (RIN 1046-38 cells) and brain-derived (NMB7) cells in culture; the exon A promoter exhibits greater activity in islet cells, whereas the exon B promoter more efficiently activates transcription in neuronal cells. Mutation of a CREB site within the ICA1 exon B promoter significantly enhances transcriptional activity in both cell lines. Our basic understanding of expression from the functional core promoter elements of ICA1 is an important advance that will not only add to our knowledge of the ICA69 autoantigen but will also facilitate a rational approach to discover the function of ICA69 and to identify relevant ICA1 promoter polymorphisms and their potential associations with disease.

Antibodies against different epitopes of heat-shock protein 60 in children with type 1 diabetes mellitus

The aim of this study was to investigate the amounts and epitope specificity of antibodies against heat shock protein 60 (hsp60) in the sera of type 1 diabetic and healthy children. Antibodies specific for peptide p277 of human hsp60 and of M. bovis as well as for human hsp60, M. bovis hsp65 proteins were measured by ELISA. Other autoantibodies (islet cell antibodies, glutamate decarboxylase antibodies and IA-2 antibodies) were also determined. A total number of 83 serum samples from children with type 1 diabetes mellitus and 81 samples of control children were investigated. Epitope scanning of the hsp60 for linear antibody epitopes was carried out using synthetic peptides attached to pins. The antibody levels specific for peptide p277 of human- and of M. bovis origin were significantly (human: P=0.0002, M. bovis: P=0.0044) higher in the diabetic children group than in the healthy children. We could not find significant difference in the antibody levels to whole, recombinant hsp proteins among the examined groups of children. Antibodies to two epitope regions on hsp60 (AA394-413 and AA435-454) were detected in high titres in sera of children with diabetes mellitus. The first region similar to the sequence found in glutamate decarboxylase, whereas the second one overlaps with p277 epitope to a large extent. Presence of antibodies to certain epitopes of hsp60 (AA394-413-glutamic acid decarboxylase-like epitope; AA435-454-p277-like epitope) in diabetic children may reflect their possible role in the autoimmune diabetogenic process of the early diabetes.

The diabetes autoantigen ICA69 and its Caenorhabditis elegans homologue, ric-19, are conserved regulators of neuroendocrine secretion

ICA69 is a diabetes autoantigen with no homologue of known function. Given that most diabetes autoantigens are associated with neuroendocrine secretory vesicles, we sought to determine if this is also the case for ICA69 and whether this protein participates in the process of neuroendocrine secretion. Western blot analysis of ICA69 tissue distribution in the mouse revealed a correlation between expression levels and secretory activity, with the highest expression levels in brain, pancreas, and stomach mucosa. Subcellular fractionation of mouse brain revealed that although most of the ICA69 pool is cytosolic and soluble, a subpopulation is membrane-bound and coenriched with synaptic vesicles. We used immunostaining in the HIT insulin-secreting beta-cell line to show that ICA69 localizes in a punctate manner distinct from the insulin granules, suggesting an association with the synaptic-like microvesicles found in these cells. To pursue functional studies on ICA69, we chose to use the model organism Caenorhabditis elegans, for which a homologue of ICA69 exists. We show that the promoter of the C. elegans ICA69 homologue is specifically expressed in all neurons and specialized secretory cells. A deletion mutant was isolated and found to exhibit resistance to the drug aldicarb (an inhibitor of acetylcholinesterase), suggesting defective neurotransmitter secretion in the mutant. On the basis of the aldicarb resistance phenotype, we named the gene ric-19 (resistance to inhibitors of cholinesterase-19). The resistance to aldicarb was rescued by introducing a ric-19 transgene into the ric-19 mutant background. This is the first study aimed at dissecting ICA69 function, and our results are consistent with the interpretation that ICA69/RIC-19 is an evolutionarily conserved cytosolic protein participating in the process of neuroendocrine secretion via association with certain secretory vesicles.

Milk and diabetes

Type 1 diabetes is based on autoimmunity, and its development is in part determined by environmental factors. Among those, milk intake is discussed as playing a pathogenic role. Geographical and temporal relations between type 1 diabetes prevalence and cow's milk consumption have been found in ecological studies. Several case-control studies found a negative correlation between frequency and/or duration of breast-feeding and diabetes, but this was not confirmed by all authors. T-cell and humoral responses related to cow's milk proteins were suggested to trigger diabetes. The different findings of studies in animals and humans as well as the potential underlying mechanisms with regard to single milk proteins (bovine serum albumin, beta-lactoglobulin, casein) are discussed in this review. In contrast to type 1 diabetes, the etiology of type 2 diabetes, characterized by insulin resistance is still unclear. In a population with a high prevalence of type 2 diabetes, the Pima Indians, people who were exclusively breastfed had significantly lower rates of type 2 diabetes than those who were exclusively bottlefed. Studies in lactovegetarians imply that consumption of low fat dairy products is associated with lower incidence and mortality of diabetes and lower blood pressures. In contrast, preference for a diet high in animal fat could be a pathogenic factor, and milk and high fat dairy products contribute considerably to dietary fat intake. Concerning milk fat composition, the opposite effects of various fatty acids (saturated fatty acids, trans-fatty acids, conjugated linoleic acid) in vitro, in animals and in humans have to be considered.

Production of the islet cell antigen ICA69 (p69) with baculovirus expression system: analysis with a solid-phase time-resolved fluorescence method of sera from patients with IDDM and rheumatoid arthritis

Islet cell antigen 69 (ICA69), previously implicated as an autoantigen in autoimmune insulin-dependent diabetes mellitus (IDDM), was produced using baculovirus-mediated expression in Spodopterafrugiperda (Sf9) insect cells. In these cells the protein was effectively expressed and ICA69 carrying C-terminal histidine-hexapeptide could be efficiently purified using immobilized metal chelate affinity chromatography. Screening of patient and control sera using this protein as an antigen in time-resolved fluoroimmunoassay (TR-FIA) identified 4/50 of patients with IDDM and 6/73 of patients with rheumatoid arthritis (RA) to be positive for ICA69 antibodies. The number of positives did not differ significantly between patients and control subjects but the level of binding was higher in sera from RA patients compared to that of control sera (P = 0.003). The results show that some subjects have specific autoreactive antibodies against the ICA69 protein produced with recombinant technology.

Autoimmune events during interferon beta-1b treatment for multiple sclerosis

Autoimmune events, although rarely reported during interferon beta-1b (IFNB) treatment of relapsing-remitting (RR) multiple sclerosis (MS), may be more frequent than expected due to the many immunologic abnormalities associated with this disease. We report the prospective two-year follow-up of autoimmune events in 40 RR MS patients treated with IFNB and in 21 untreated MS controls. Thyroid and liver function and serum level of 12 autoantibodies (autoAbs) against organ- (thyroid, gastric, pancreatic) and non-organ-specific antigens were serially monitored. In contrast to control patients, autoAbs (anti-nuclear, -smooth muscle or -thyroid antigens) were detected in 13 IFNB-treated patients, and these were associated with thyroid or liver function alteration in many cases. Persistent autoimmune thyroid dysfunction occurred in three IFNB-treated patients, all of whom were women with a familial history of thyroid disease or baseline anti-thyroid autoAb positivity. For improvement of the MS relapse rate, thyroid dysfunction was adequately treated without stopping IFNB. Liver function alteration (17 IFNB-treated patients, associated with non-organ-specific autoAbs in four) was transient and did not require IFNB treatment to be stopped, with the exception of one patient who was already suffering from a drug-induced hepatopathy at baseline. During the IFNB treatment of MS, several autoimmune events may occur, indicating that thyroid and liver function and autoAbs must be carefully monitored.

Effect of experimental diabetes mellitus and arthritis on the pharmacokinetics of hydroxychloroquine enantiomers in rats

PURPOSE

To study the effect of experimental diabetes and arthritis on the pharmacokinetics of hydroxychloroquine (HCQ) enantiomers in rats.

METHODS

The pharmacokinetic studies were carried out following administration of 40 mg/kg of racemic HCQ to diabetic, insulin-treated diabetic, adjuvant arthritic and control rats.

RESULTS

Renal (70% and 62% for R- and S-HCQ, respectively) and non-renal clearance (100% and 145% for R- and S-HCQ, respectively) of HCQ enantiomers were significantly increased in diabetic rats. Diabetes-induced alterations in the disposition of HCQ were reversed by insulin treatment. In arthritic rats, systemic clearance (CL) of HCQ enantiomers was significantly reduced (1.05 +/- 0.15 and 1.3 +/- 0.19 l/h/kg for R- and S-HCQ, respectively) compared to controls (1.69 +/- 0.32 and 1.93 +/- 0.34 l/h/kg for R- and S-HCQ, respectively). The fraction unbound of the R- and S-HCQ were 49.4% and 50.5% lower in platelet rich plasma of arthritic rats compared to healthy rats. Increased blood concentrations of HCQ enantiomers in arthritic rats were significantly related to the degree of inflammation.

CONCLUSIONS

Diabetes significantly increased the CL of both R- and S-HCQ by increasing renal and non-renal clearance. Arthritis caused a significant decrease in CL of HCQ enantiomers through increased binding and a decreased intrinsic clearance. The effect of the diseases on the pharmacokinetics of HCQ, however, was not stereoselective.

Cross-reacting idiotypes on anti-insulin autoantibodies in autoimmune diseases, identified by monoclonal antibodies

Investigations on the specific idiotypes of autoantibodies are supposed to help with the understanding of the control mechanisms participating in the pathogenesis of autoimmune diseases. This study describes three monoclonal antibodies (Mabs) that recognize distinct idiotypic determinants on anti-insulin autoantibodies. The preabsorption by IAA-positive sera of insulin inhibits their subsequent binding to the anti-Id, thus suggesting that the Mabs recognize epitopes located at or near the binding site of insulin autoantibodies (IAA). These idiotypes are detected in sera from patients with insulin-dependent diabetes mellitus (IDDM), which are IAA-negative, also. It is possible that the expression of the idiotypes recognized might generally be associated with induction of autoantibodies, since they were found in sera from patients with rheumatoid arthritis (RA), autoimmune thyroid disease (AITD), and cataract (K). It can be assumed that the corresponding idiotypes of these Mabs, or similar structures (sequential or conformational), are expressed on autoantibodies with various antigen-binding specificities. These data suggest that some autoimmune diseases are preceded by the secretion of autoantibodies which express a common or similar pathological idiotype.

Th1-like cytokine production profile and individual specific alterations in TCRBV-gene usage of T cells from newly diagnosed type 1 diabetes patients after stimulation with beta-cell antigens

In order to study cytokine production profile (IFN-gamma, IL-4 and TNF-alpha) and TCRBV-gene usage of peripheral autoreactive T cells from IDDM patients, we have generated antigen-specific T cell lines with either tetanus toxoid, insulinoma membranes or a single beta-cell protein, recombinant ICA69, which has been shown to be a target of both autoantibodies and T cells in IDDM. By semi-quantitative polymerase chain reaction (PCR) analysis, we have determined the composition of the T cell receptor repertoire of these T cell lines and compared this with the general peripheral repertoire. T cell responses against beta-cell antigens and tetanus toxoid (TT) were shown to be associated with IFN-gamma and TNF-alpha production, suggestive of a Th1-like phenotype of the T-cell lines. The production of IFN-gamma was significantly higher in T-cell lines generated with ISG compared to those generated with TT. The cytokine production profiles of the T-cell lines generated with ICA69 did not provide an obvious explanation for the inverse relation between cellular and humoral responses to this protein observed earlier. Upon stimulation with beta-cell antigens, outgrowth of T cells using a restricted set of TCRBV elements was observed in newly diagnosed IDDM patients. However, this skewing in TCRBV-gene expression was patient-specific rather than antigen-associated, since the T-cell repertoire that is used for the recognition of these antigens was, overall, heterogeneous.

Islet cell antigens in the prediction and prevention of insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) is associated with both antibody and T-cell autoimmunity to pancreatic islet cell components. In recent years, considerable progress has been made in the identification of the molecular components of the pancreatic islets to which these immune responses are directed. These advances have led to the development of a number of immune markers for use in screening for individuals at risk for disease, and there is promise of antigen-specific immune intervention therapies to prevent diabetes in those identified as at risk. In this article, we review our current knowledge of autoantigens associated with IDDM and the implications this has on the prediction and prevention of the disease.

Insulin-dependent diabetes mellitus associated with autoimmune thyroiditis and rheumatoid arthritis

A case associated with insulin-dependent diabetes mellitus (IDDM), rheumatoid arthritis (RA), and autoimmune thyroid disease (AITD) was reported. A high titer of anti-glutamic acid decarboxylase antibody (GAD) and a positive islet cell antigen were observed. The patient's human leukocyte antibody (HLA) haplotype was a homozygote of DQA1*0301, DQB1*0401, and DRB1*0405. Because this haplotype was in linkage disequilibrium with DPB1*0501, an allele associated with AITD in Japanese patients, the patient was homozygous for alleles susceptible to IDDM, RA, and AITD. A specific HLA haplotype susceptible to several autoimmune disease may result in the development of IDDM, RA, and AITD.

HLA-associated inverse correlation between T cell and antibody responsiveness to islet autoantigen in recent-onset insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) is a T cell-dependent immune-mediated disease. Recently, a novel islet cell antigen (ICA69) recognized by autoantibodies was described. We tested T cell responsiveness to ICA69 in peripheral blood of patients with recent onset IDDM (n = 46), patients with long-standing IDDM (n = 44), non-diabetic age-matched, islet cell autoantibody- and glutamic acid decarboxylase (GAD)65 antibody-negative first-degree relatives of IDDM patients (n = 15) and rheumatoid arthritis patients (n = 22). T cell responsiveness was significantly higher in recent onset IDDM patients, compared to IDDM patients post-disease onset, non-diabetic first degree relatives and rheumatoid arthritis patients (p < 0.001). In responding IDDM patients a significant inverse correlation between T cell and autoantibody responsiveness to ICA69 was observed (p < 0.0005). Immunogenetic evaluation revealed an association of HLA-DR3 with T cell responsiveness to ICA69 (p < 0.02) and absence of ICA69-reactive autoantibodies (p < 0.04). The increased T cell reactivity to ICA69 in the absence of antibody reactivity at onset of IDMM is associated with an HLA class II immune response gene, and therefore suggestive of a genetically controlled selective activation of T helper subsets to a specific autoantigen in humans.

ICA69 is expressed equally in the human endocrine and exocrine pancreas

Islet cell autoantigen 69 kDa (ICA69) has been reported as a polypeptide antigen expressed in pancreatic beta cells, and autoimmunity against this antigen has been associated with insulin-dependent diabetes mellitus. We have studied the cell type specificity and ontogeny of ICA69 gene expression in man. The ICA69 gene was expressed in all adult human tissues. The level of expression was three-to five-times higher in the pancreas than in the brain, liver, intestine, kidney, spleen, lung or adrenal glands. Pancreatic ICA69 expression increased with age, adult levels being five times higher than the levels present at 13 weeks of gestation. Total RNA from four separate preparations of isolated human islets revealed levels of ICA69 mRNA similar to those found in the pancreas as a whole, although another islet antigen, glutamic acid decarboxylase 65, was highly enriched in the islets. In situ hybridization and immunohistochemical staining of sections of the fetal and adult pancreas revealed expression of the ICA69 gene and protein throughout the acinar, ductal, and islet tissue, but not in the mesenchyme. Analysis of ICA69 mRNA levels in human cell lines indicated expression in neural, endothelial and epithelial cells, but not in fibroblasts. In conclusion, ICA69, although highest in the pancreas, is widely distributed in other human tissues, excluding connective tissue. Within the human pancreas, ICA69 is not enriched in the islets or in the beta cells.