HLA-DR4–Associated T and B Cell Responses to Specific Determinants on the IA-2 Autoantigen in Type 1 Diabetes

Abstract

Autoantibodies to IA-2 in type 1 diabetes are associated with HLA-DR4, suggesting influences of HLA-DR4–restricted T cells on IA-2–specific B cell responses. The aim of this study was to investigate possible T–B cell collaboration by determining whether autoantibodies to IA-2 epitopes are associated with T cell responses to IA-2 peptides presented by DR4. T cells secreting the cytokines IFN-γ and IL-10 in response to seven peptides known to elicit T cell responses in type 1 diabetes were quantified by cytokine ELISPOT in HLA-typed patients characterized for Abs to IA-2 epitopes. T cell responses were detected to all peptides tested, but only IL-10 responses to 841–860 and 853–872 peptides were associated with DR4. Phenotyping by RT-PCR of FACS-sorted CD45ROhi T cells secreting IL-10 in response to these two peptides indicated that these expressed GATA-3 or T-bet, but not FOXP3, consistent with these being Th2 or Th1 memory T cells rather than of regulatory phenotype. T cell responses to the same two peptides were also associated with specific Abs: those to 841–860 peptide with Abs to juxtamembrane epitopes, which appear early in prediabetes, and those to peptide 853–872 with Abs to an epitope located in the 831–862 central region of the IA-2 tyrosine phosphatase domain. Abs to juxtamembrane and central region constructs were both DR4 associated. This study identifies a region of focus for B and T cell responses to IA-2 in HLA-DR4 diabetic patients that may explain HLA associations of IA-2 autoantibodies, and this region may provide a target for future immune intervention to prevent disease.