TOP1 and systemic sclerosis: Two further individuals carried HLA-DRB1*15:01 and *16:01, alleles with no previously reported ATA + SSc association, but which contained identical peptide-contact motifs to ATA−associated alleles, and shared TOP1 epitopes isolated from all such alleles elicited CD4+ T cell activation in 73% of ATA + SSc patients relative to 27% of ATA−patients (Tiniakou et al., 2020).