Taken together, these results show that PD-1 was expressed in a fraction of CD56dim CD16+ NK cells in KS patients, and to a lesser extent in patients with chronic viral infections (HHV8, HIV or HCV), without clear relationship between the proportion of PD-1pos NK cells and clinical or biological characteristics of the underlying disease (duration, activity, response to treatment, viral load, associated infection). Here, PDCD1 is linked to Kaposi's sarcoma.