PTPRN and type 1 diabetes mellitus: For the IA-2 autoantigen, relationships between HLA-DRB1*04 expression, the detection of T cell responses to specific IA-2 peptides and the presence of autoantibodies to specific regions of the antigen provide evidence of close links of HLA alleles with both T cell and B cell responses to a major autoantigen in type 1 diabetes [6].