Additionally, stimulation with PMA changed the CTLA-4 protein expression in healthy lymphocytes compared to a lack of such a response in CLL; the significant increase in the levels of this protein has been demonstrated (primarily in T cell populations) and is consistent with the well-known impact of activation on CTLA-4 gene induction [37]. The gene discussed is CTLA4; the disease is B-cell chronic lymphocytic leukemia.