HLA-DRB1 and myeloid sarcoma: Further studies show that increased risk of MS is specifically linked to antibody responses against the amino acid 385–420 region of EBNA1,23, 24 that individuals without an EBNA1 antibody response became positive prior to MS onset7 and that EBNA1 antibody titres are associated with HLA‐DRB1*15: 01 – the strongest genetic risk factor for MS.25, 26