Increased expression of PD1, CD160, and CD244 on CD8⁺ T cells from patients with CLL. The expression of (A) CD244, (B) CD160, and (C) PD1 were assessed on CD8⁺ T cells from patients with CLL and healthy age-matched controls. Significant increases in both the proportion, and the absolute number, of T cells expressing these molecules were observed. (D) PD1 expression identified a population of CD3⁺CD8⁺ T cells with high expression of BLIMP1, which are expanded in CLL. (E) Flow cytometric plots showing the presence of this CD3⁺CD8⁺PD1⁺BLIMP1^HI population that is increased in CLL patients. (F) Expression of CD127 is not significantly down-regulated on CLL T cells.