Altered Systemic and Intestinal IgA Immune Responses in Individuals With Type 1 Diabetes

Increasing evidence supports the observation that immunoglobulin A (IgA) exerts a critical effect on the susceptibility to autoimmunity by modulating gut homeostasis and subsequent host immunity. We hypothesized that the IgA immunity is altered in individuals with type 1 diabetes. To test our hypothesis, we investigated intestinal, oral, and peripheral IgA immune responses in individuals with type 1 diabetes.

We collected stool, oral cavity, and blood samples from participants diagnosed with type 1 diabetes (within 1 year and more than 1 year) and healthy control individuals. Serum islet autoantibody titers were detected by radioligand assays. IgA-bound bacteria and IgA-expressing B cells were studied by flow cytometry. Oral free IgA level was measured by enzyme-linked immunosorbent assay. Serum and stool free IgA concentrations were determined by immune-turbidimetry method.

Individuals diagnosed with type 1 diabetes within 1 year had an increased proportion of stool IgA-bound bacteria compared with healthy control individuals. The proportion of stool IgA-bound bacteria was positively associated with glutamic acid decarboxylase autoantibody titer. Moreover, individuals with a longer disease duration displayed a higher level of IgA-bound bacteria than those diagnosed within 1 year. In contrast to healthy control individuals, type 1 diabetes patients had increased serum IgA concentrations.

Individuals with type 1 diabetes display altered IgA immunity, especially increased stool IgA-bound bacteria, which is likely to contribute to β-cell autoimmunity and the disease development, and thus, might be considered as a novel therapeutic target for the treatment of type 1 diabetes.