By secreting chemokines, such as CXCL12 and CXCL13, and growth factors, such as B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL), activated microglia and astrocytes could create a CNS microenvironment in people with MS that is conducive to the accumulation and survival of memory B cells and plasma cells [11]. The gene discussed is TNFSF13B; the disease is myeloid sarcoma.