Induction of Diabetes-Related Autoantibodies below Cutoff for “Positivity” in Young Nondiabetic Children

The importance of CTLA-4 polymorphism and human leukocyte antigen genotype for the induction of diabetes-associated cytokine response in healthy school children

BACKGROUND

Type 1 diabetes (T1D) is an autoimmune disease associated with the destruction of pancreatic beta cells and genetically linked to human leukocyte antigen (HLA) class II DR3-DQ2 and DR4-DQ8 haplotypes. The +49A/G polymorphism of the immunoregulatory cytotoxic T-lymphocyte antigen 4 (CTLA-4) gene is also associated with T1D. Genetic and environmental risk factors precede the onset of T1D, which is characterized by a T helper 1 cell-dominating cytokine response to diabetes-related autoantigens.

AIM

To investigate immunological differences between healthy children with and without CTLA-4 +49A/G and HLA genetic susceptibility for T1D.

STUDY DESIGN

Young, 7-15 years of age, healthy subjects (n = 58) were investigated to test whether CTLA-4 +49A/G genotype was associated with enzyme-linked immunospot assay T-cell responses to T1D-related autoantigens. Because T1D is primarily HLA-DQ associated, we stratified the healthy subjects by HLA genotypes associated with the disease.

RESULTS

Peptide of heat shock protein 60 induced a higher interferon-gamma (IFN-gamma) response in subjects with risk-associated CTLA-4 polymorphism (GG genotype) (p = 0.02) while glutamic acid decarboxylase 65-induced interleukin-4 (IL-4) secretion was lower in GG genotype subjects (p = 0.02).

CONCLUSION

The increased IFN-gamma response and lower IL-4 response toward diabetes-related autoantigens shown in CTLA-4 +49 GG risk subjects show a possible mechanism for the association between CTLA-4 and T1D.

Demonstration of natural autoantibodies against the neurofilament protein α-internexin in sera of patients with endocrine autoimmunity and healthy individuals

Serum anti-pituitary antibodies (APAs) to cytosolic antigens have been found in association with autoimmune hypophysitis, idiopathic hypopituitarism, and other autoimmune endocrinopathies. Here, an immunoblot method was used to search for serum autoantibody (AAb) reactivities against pituitary antigens, including nuclear and cytoskeletal proteins, in six patients with idiopathic hypopituitarism, 60 patients with type 1 diabetes, nine patients with autoimmune polyglandular syndrome (APS) type 1, and in 74 healthy controls. Frequent patient serum IgG reactivity was observed against a 60 kDa human pituitary antigen, and the cross-reactive 62 kDa protein from rat brain was identified as alpha-internexin (alpha-INX) by proteomic methods. IgG and IgM AAbs to this neuron-specific type IV intermediate filament (IF) protein were found in most sera of patients with endocrine autoimmunity as well as healthy subjects with no significant differences in frequencies between the groups, but the levels of IgM alpha-INX AAbs were higher in patients with hypopituitarism as compared to healthy controls (P = 0.032, Mann-Whitney U-test). These findings suggest that alpha-INX AAbs are not specifically related to autoimmune endocrine diseases and most probably are a part of the natural AAb repertoire. This is the first demonstration of alpha-INX AAbs as one of the predominant neuronal IF AAbs in human sera.

Cow-milk-free diet during last trimester of pregnancy does not influence diabetes-related autoantibodies in nondiabetic children

The aim was to study whether cow-milk-free diet during the last trimester of pregnancy influences the development of diabetes-related autoantibodies in nondiabetic children. We also examined the effect of later introduction of cow milk proteins and gluten. Blood samples were taken from 205 children at 6 weeks, 6 months, 18 months, and 5 years, whose mothers had been randomized to either a cow-milk-free diet or not during the last trimester of pregnancy. During the first 3 months of life, cow milk proteins were not fed to the children. Autoantibodies against GAD.(65) (GADA), tyrosine phosphatase (IA-2A), and insulin (IAA) were determined by a radioligand-binding assay. We found specific autoantibodies, although in low concentrations below the traditional cutoff for positivity in the children. The diet of the mother during pregnancy had no influence on development of autoantibodies, nor did duration of breast-feeding or time for introduction of gluten. Cow milk introduction between 3 and 6 months caused a transient increase in GADA at 6 months of age (p < 0.05). Children who developed atopic disease had significantly lower IA-2A at 6 months (p < 0.001).