We present the data of possible epitopes for the most common HLA-DR alleles expressed in Caucasians (DR4, DR1, and DR11 [26]) in Table S2, although other alleles (i.e., DR3, DR16, DR15 and DRB5, which are linked to SLE [27]), appeared able to bind more than one CXCL4-derived epitope (not shown). Here, PF4 is linked to systemic lupus erythematosus.