Functional relevance for disease predisposition was further supported for the CYBB gene, by microarray analysis in CD4+/− mononuclear cells of 21 individuals from five Finnish multiplex MS families, as well as by real-time RT-PCRs performed on RNA extracted from peripheral blood mononuclear cells of an Italian replication cohort of 21 MS cases and 21 controls. Here, CD4 is linked to myeloid sarcoma.