PDCD1 and Kaposi's sarcoma: PD‐1, a member of the co‐signaling B7 family, plays a role in downregulating NK cell immunity against hematological tumors.47 Previous research suggested that PD‐1 expression could be a marker of NK cell functional exhaustion in patients with Kaposi sarcoma.48 Further, a recent report indicated that PD‐1 expression on NK cells is crucial for innate immune regulation against tumors.47 To our knowledge, no other endogenous factors have been shown to modulate PD‐1 expression on NK cells.