Immunological studies on type 1 diabetes in identical twins

Twin studies in autoimmune disease: genetics, gender and environment

Twin studies are powerful tools to discriminate whether a complex disease is due to genetic or environmental factors. High concordance rates among monozygotic (MZ) twins support genetic factors being predominantly involved, whilst low rates are suggestive of environmental factors. Twin studies have often been utilised in the study of systemic and organ specific autoimmune diseases. As an example, type I diabetes mellitus has been investigated to establish that that disease is largely affected by genetic factors, compared to rheumatoid arthritis or scleroderma, which have a weaker genetic association. However, large twin studies are scarce or virtually non-existent in other autoimmune diseases which have been limited to few sets of twins and individual case reports. In addition to the study of the genetic and environmental contributions to disease, it is likely that twin studies will also provide data in regards to the clinical course of disease, as well as risk for development in related individuals. More importantly, genome-wide association studies have thus far reported genomic variants that only account for a minority of autoimmunity cases, and cannot explain disease discordance in MZ twins. Future research is therefore encouraged not only in the analysis of twins with autoimmune disease, but also in regards to epigenetic factors or rare variants that may be discovered with next-generation sequencing. This review will examine the literature surrounding twin studies in autoimmune disease including discussions of genetics and gender.

Comparison of cytokine ELISpot assay formats for the detection of islet antigen autoreactive T cells

The identification of sensitive assay formats capable of distinguishing islet autoreactive T cells directly ex vivo in blood is a major goal in type 1 diabetes research. Recently, much interest has been shown in the cytokine enzyme linked immunospot assay (CK ELISpot), an assay potentially capable of fulfilling these difficult criteria. To address the utility of this assay in detecting autoreactive T cells, a 'wet' workshop was organized using the same fresh blood sample and coded antigens. Five different laboratories participated, using three distinct CK ELISpot assay formats. Samples from two subjects were pre-tested for responses to sub-optimal concentrations of tetanus toxoid, representing a low frequency recall response, and peptides from diabetes associated autoantigens GAD65, IA-2 and HSP60. All participants measured interferon-gamma production and combinations of interleukins-4, -5, -10 and -13. In the workshop 4 of 5 laboratories detected low frequency recall responses in both subjects and 3 of 5 detected at least one of the autoreactive peptide responses concordant with pre-testing. Significant assay format related differences in sensitivity and signal-to-noise ratio were observed. The results demonstrate the potential for detection of low-level autoreactive T cell responses and identify assay characteristics that will be useful for studies in type 1 diabetes.

The role of T-cells in the pathogenesis of Type 1 diabetes: from cause to cure

Type 1 diabetes mellitus results from a T-cell mediated autoimmune destruction of the pancreatic beta cells in genetically predisposed individuals. The knowledge of the immunopathogenesis has increased enormously in the last two decades. The contribution of T-cells in the pathogenesis is beyond doubt. Therapies directed against T-cells have been shown to halt the disease process and prevent recurrent beta-cell destruction after islet transplantation. Less is known about the nature and function of these T-cells, the cause of the loss of tolerance to islet autoantigens, why the immune system apparently fails to suppress autoreactivity, and whether (or which) autoantigen(s) are critically involved in the initiation or progression of the disease. The contribution of dendritic cells in directing the immune response is clear, while the contribution of B-cells and autoantibodies is subject to reconsideration. Autoreactive T-cells have proven to be valuable tools to study pathogenic or diabetes-related processes. Measuring T-cell autoreactivity has also provided critical information to determine the fate of islet allografts transplanted to Type 1 diabetic patients. Cellular autoimmunity is a difficult study subject, but it has been a worthwhile quest to unravel the role of T-cells in the pathogenesis of Type 1 diabetes. The challenge for the future is to determine which factors contribute to the loss of tolerance to beta-cell antigens, and to define what measures T-cells can provide to suppress autoreactivity, since it is becoming increasingly evident that T-cells provide a two-edged sword: some T-cells could be pathogenic, but others can regulate the disease process and thus form new targets for immunointervention.

Evaluation of the pancreas reserve in siblings of type I diabetic children

INTRODUCTION

The purpose of this study was to determine the pancreas reserve in siblings of diabetic patients by screening islet cell antibodies (ICA), insulin auto antibodies (IAA), reduced C-peptide levels, first-phase insulin release and the derangement of cellular immunity (reduction of natural killer cells, abnormality of the T cell subpopulations).

METHODS AND RESULTS

Twelve siblings (aged 9.3 +/- 2.8 years) of diabetic children were evaluated and results were compared with the control group (12.1 +/- 3.5 years). For siblings of the diabetic children, fasting, post-prandial and glucagon response C-peptide mean values were 2.2 +/- 1.2, 7.2 +/- 7.1 and 5.3 +/- 3.6 ng/mL, respectively, while in the control group they were 1.5 +/- 0.8, 3.6 +/- 2.0 and 5.1 +/- 2.9 ng/mL, respectively. There were no differences between the two groups. In 33%, postprandial C-peptide, and in 11% of the siblings, glucagon response C-peptide values were exaggerated. In siblings the first phase insulin release (FPIR) during an intravenous glucose tolerance test was 128.5 +/- 96.6 (above the 50th percentile) and stimulated insulin release (SIR) was 103.8 +/- 92.5 (above 25th percentile). Sibling values were significantly lower than the control group (FPIR 152.4 +/- 42.5, P = 0.01; SIR 134.9 +/- 38.2, P = 0.01). Values for FPIR (in two children) and SIR (three cases) were below the 5th percentile. In one, FPIR and SIR levels were both below the 1st percentile. Islet cell antibodies and IAA were also present in this subject. Treatment with nicotinamide was started in the cases with FPIR and SIR below the 5th percentile. We did not observe overt diabetic symptoms during the follow-up period of more than 3 years.

CONCLUSION

We recommend that borderline insulin secretion be tested annually in siblings who show insufficient FPIR.

Primary and secondary liver/kidney microsomal autoantibody response following infection with hepatitis C virus

Liver/kidney microsomal autoantibody type 1 (LKM-1), which characterizes a subtype of autoimmune hepatitis, is also found in some patients with chronic hepatitis C virus (HCV) infection. Whether HCV and LKM-1 are accidentally or causally related is unknown. This case report describes a child who became infected by HCV after liver transplantation for end-stage liver disease caused by alpha 1-antitrypsin deficiency. LKM-1 was detected by immunofluorescence, anti-microsomal reactivity by Western blotting, anti-HCV and anti-GOR by immunoenzymatic assays, and HCV RNA by polymerase chain reaction. Two weeks after HCV infection, immunoglobulin (Ig) M LKM-1 appeared, followed by IgG1 LKM-1, with titers increasing to 1/2560; antibodies to a 50-kilodalton liver microsomal protein appeared 2 months later. Sera from day 1 posttransplant became positive for HCV RNA. HCV RNA was also detected in a liver biopsy specimen obtained 3 months after surgery. The patient did not produce anti-HCV and anti-GOR antibodies throughout the study and had no histological evidence of hepatitis. The temporal relationship between HCV infection and LKM-1 production suggests that HCV may trigger a primary autoimmune response. The lack of liver damage attributable to autoimmunity or viral infection may be caused by immunosuppression.