Since the majority of B cells identified within the CNS of MS patients belong to the memory B cell pool [15–17], we further sorted the SPMS B cells into memory (CD27+ IgD−/+), naive (CD27− IgD+), and transitional (CD24high CD38high) B cell subsets (Fig. 4a) prior to exposing them to astrocyte-soluble factors. The gene discussed is CD27; the disease is myeloid sarcoma.