Based on studies, DR2α is an important etiologic risk factor of MS.3-5 Recent survey in humanized mice shows functional epistatic interactions whereby DRB5*0101 directly modulates the severity of MS through activation-induced cell death (AICD) of encephalitogenic T cells which are restricted by HLA-DRB1*1501 allele.6 The gene discussed is HLA-DRB5; the disease is myeloid sarcoma.