A Hybrid Insulin Epitope Maintains High 2D Affinity for Diabetogenic T Cells in the Periphery

Diabetes. 2020 Mar;69(3):381-391. doi: 10.2337/db19-0399. Epub 2019 Dec 5.


β-Cell antigen recognition by autoreactive T cells is essential in type 1 diabetes (T1D) pathogenesis. Recently, insulin hybrid peptides (HIPs) were identified as strong agonists for CD4 diabetogenic T cells. Here, using BDC2.5 transgenic and NOD mice, we investigated T-cell recognition of the HIP2.5 epitope, which is a fusion of insulin C-peptide and chromogranin A (ChgA) fragments, and compared it with the WE14 and ChgA29 -42 epitopes. We measured in situ two-dimensional affinity on individual live T cells from thymus, spleen, pancreatic lymph nodes, and islets before and after diabetes. Although preselection BDC2.5 thymocytes possess higher affinity than splenic BDC2.5 T cells for all three epitopes, peripheral splenic T cells maintained high affinity only to the HIP2.5 epitope. In polyclonal NOD mice, a high frequency (∼40%) of HIP2.5-specific islet T cells were identified at both prediabetic and diabetic stages comprising two distinct high- and low-affinity populations that differed in affinity by 100-fold. This high frequency of high- and low-affinity HIP2.5 T cells in the islets potentially represents a major risk factor in diabetes pathogenesis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibody Affinity / immunology
  • C-Peptide / immunology*
  • CD4-Positive T-Lymphocytes / immunology*
  • Chromogranin A / immunology*
  • Diabetes Mellitus, Type 1 / genetics
  • Diabetes Mellitus, Type 1 / immunology*
  • Epitopes, T-Lymphocyte / immunology*
  • Islets of Langerhans / cytology
  • Lymph Nodes / cytology
  • Mice
  • Mice, Inbred NOD
  • Mice, Transgenic
  • Peptide Fragments / immunology*
  • Receptors, Antigen, T-Cell / genetics
  • Spleen / cytology
  • T-Lymphocytes / cytology
  • T-Lymphocytes / immunology
  • Thymocytes / cytology
  • Thymocytes / immunology
  • Thymus Gland / cytology


  • C-Peptide
  • Chromogranin A
  • Epitopes, T-Lymphocyte
  • Peptide Fragments
  • Receptors, Antigen, T-Cell
  • WE14 protein, mouse