Ex‐vivo activation of B cells stimulates CD4 and CD8 proliferation and pro‐inflammatory activation, whilst B cell depletion diminishes the capacity of CD4+ cells from MS patients to be stimulated through an MHC II/HLA‐DR15 B cell‐to‐ CD4+ T cell interaction (4, 26, 42). The gene discussed is CD8A; the disease is myeloid sarcoma.