CD19 and B-cell chronic lymphocytic leukemia: Although the underlying role of CD19 in the activation and differentiation of B cells is undeniable and its highly conserved expression is observed in most B cell malignancies, such as acute lymphoblastic leukemias (ALL), chronic lymphocytic leukemias, and lymphomas, it is still unknown whether CD19 is directly involved in B cell carcinogenesis or not.95