Oral Presentation Australasian Society for Immunology Annual Scientific Meeting 2014

Dissecting the function of human CD4+ T cells in autoimmune diabetes (#107)

Stuart I Mannering 1 , Janine P Kuehlich 1 , Peter D Campbell 1 , Balasubramanian Krishnamurthy 1 , Thomas Loudovaris 1 , P.Toby H Coates 2 , Thomas C Bridnicki 1 , Philip J O'Connell 3 , Katerine Kedzierska 4 , Christine Rodda 5 , Philip Bergman 6 , Erin Hill 6 , Anthony W Purcell 7 , Nadine L Dudek 7 , Helen E Thomas 1 , Thomas WH Kay 1
  1. Immunology and Diabetes Unit, St. Vincent’s Institute of Medical Research, Fitzroy, Vic
  2. Dept of Medicine, University of Adelaide, Adelaide, SA, Australia
  3. National Pancreas Transplant Unit, University of Sydney at Westmead Hospital, Sydney, NSW, Australia
  4. Dept of Microbiology and Immunology, University of Melbourne, Parkville, Vic
  5. University of Melbourne, North West Academic Centre, Sunshine Hospital, St Albans, VIC, Australia
  6. Dept of Paediatrics, Monash University, Clayton, VIC, Australia
  7. Dept of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia

The molecular basis of autoimmune disease remains enigmatic. Type 1 diabetes (T1D) is an autoimmune disease caused by the T-cell mediated destruction of the insulin-producing beta cells. The HLA genes, HLA-DQ8 and HLA-DQ2, confer the highest risk of developing T1D implicating CD4+ T-cell responses in the pathogenesis of T1D. Efforts to analyze CD4+ T-cell responses in T1D have been hampered by the technical challenges associated with detecting these rare cells in patient blood. To overcome this problem we isolated T cells from the pancreatic islets from organ donors who suffered from T1D. We have focused on the CD4+ T-cells from one donor with the HLA type: HLA DR3-DQ2; DR4-DQ8 that confers very high risk of T1D. We characterized 53 CD4+ T-cell clones and found that 15 (28%) recognized epitopes derived from proinsulin C-peptide. Interestingly, most epitopes clustered in the middle of the C-peptide. Analysis of the clones’ HLA restrictions revealed that all, except one pair of clones with identical TCRs, were restricted by HLA-DQ8 (A1*03:01, B1*03:02). The remaining pair of clones were restricted by an HLA-DQ8 transdimer (DQA1*05:01, DQB1*03:02). To investigate responses to these epitopes in patients’ blood we performed CFSE-based proliferation assays. Two of eight children with recent onset T1D, but none of five HLA-matched controls had CD4+ T-cell responses to these epitopes. This is the first functional analysis of human islet-infiltrating CD4+ T cells. Our work confirms CD4+ T-cells’ role in in the pathogenesis of human T1D and links the HLA-DQ8 responses to proinsulin.