PD-1 expression on circulating and intratumoral NK cells. (A) Proportion of PD-1⁺ CD3⁻CD56⁺ NK cells in pretherapy blood in patients with cHL and DLBCL and in healthy participants. (B) Proportion of PD-1⁺ on NK-cell subsets in pretherapy blood in patients with cHL and DLBCL and in healthy participants. (C) Representative mean fluorescent intensity of PD-1 on intratumoral NK cells in patients with cHL and DLBCL (black line) and a healthy participant. Gray represents isotype control.