Chronic Lymphocytic Leukemia (CLL) is an indolent malignancy characterized by the accumulation of quiescent, immunologically dysfunctional mature B cells which are CD5 positive and that fail to undergo apoptosis, leading to leukocytosis and absolute lymphocytosis, lymphadenomegaly, and splenomegaly. Here, CD5 is linked to B-cell chronic lymphocytic leukemia.