CD19 and B-cell chronic lymphocytic leukemia: Chronic lymphocytic leukaemia (CLL)/small lymphocytic lymphoma (SLL), which is a type of NHL, is a malignancy of monoclonal, mature, antigen-experienced, and apoptosis refractory CD19+/CD5+ B lymphoid cells, detected in peripheral blood at a concentration of ≥5000 cells/μL for a period of 3 months or more (168).