CD19 and myeloid sarcoma: In MS, Bmem frequencies are elevated in the CSF compared to peripheral blood (88, 89) and Bmem comprise the majority of B cells populating the CSF (90, 91) (CD27+ IgD- (88, 91); CD19+CD27+ (89); CD27+ CD138- (90); CD19+ CD27+ IgD- and IgD+).