Some major histocompatibility complex (MHC) class II alleles predisposing to MS function as coreceptors for EBV entry into B cells [39], but other MS loci are also involved in the response to EBNA-2 [100] and there is an interaction between EBNA-1 antibody titers and HLA-DRB1*1501 [101]. Here, HLA-DRB1 is linked to myeloid sarcoma.