PDCD1 and B-cell chronic lymphocytic leukemia: However, both inhibitors reduced the expression of the inhibitory co-receptors programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA4) on T cells, as well as expression of the immunosuppressive molecules CD200, B- and T-lymphocyte attenuator (BTLA) and IL-10 by CLL cells [212].