Of note, the expression of PD-1 was significantly enhanced in healthy CTLs cultured in CLL cell-conditioned media compared to CTLs cultured in healthy B cell-conditioned media, but not that of CTLA-4 and LAG-3 (Fig. 1B, C, Supplementary Fig. 1D–F), indicating that leukemic cells indirectly suppress CTL function by releasing soluble factors that promote their exhaustion by enhancing PD-1 expression. The gene discussed is CTLA4; the disease is B-cell chronic lymphocytic leukemia.