CD19 and B-cell chronic lymphocytic leukemia: To minimize the effect on ‘bystander’ healthy B cells, Faitschuk et al. found that the IgM Fc receptor (FcμR) is better than CD19 as a promising candidate target because of its high and consistent overexpression on CD19+CD5+ CLL cells and considerably lower level of expression on nonmalignant CD19+ B cells or other hematopoietic cells.