CD19 and B-cell chronic lymphocytic leukemia: Chronic lymphocytic leukemia (CLL) is classified as a lymphoproliferative disorder characterized by the accumulation of a clonally expanded lymphocytic population with resistance to apoptosis and co-expression of CD5, CD19, and CD23 in B lymphocytes in the peripheral blood, lymph nodes, bone marrow, spleen and liver [1–4].