6 have found that, in CLL patients, expression of PD‐1 (% and MFI) on the surface of CD3+ T cell increased significantly, and lenalidomide inhibited PD‐L1/PD‐1‐mediated T‐cell dysfunction in vivo, reversing T‐cell inactivation, and thus enhancing immune function in patients. This suggests that PD‐1 high expression on CD4+ T cells in DLBCL patients may undermine T‐cell function, thereby leading to poor prognoses. Here, PDCD1 is linked to B-cell chronic lymphocytic leukemia.