HLA-DPB1 and systemic sclerosis: Negative HLA-DPB1 p1/7/9 peptide-binding groove charge (aa-55[Asp-Glu-Glu]aa-57; aa-67[Glu-Glu-Glu]aa-68; aa-82[Glu-Asp-Glu]aa-85) is associated with risk of anti-topoisomerase antibodies in systemic sclerosis[42]; negative HLA-DRB1 p4 pocket charge (aa-70[Asp-Glu]aa-71) is associated with anti-desmoglein antibodies in pemphigus vulgaris[35].