HSV-1 or UV-HSV-1 stimulates NK-dependent cytolysis of primary AML cells or cell lines but not of allogeneic healthy lymphocytes. (A) PBMCs exposed, or not, to UV-HSV-1 (0.1 pfu/PBMC for 16 hours) were added to primary AML cells (30:1 effector:target) cultured on MSC feeder layers (except 3, which was cultured alone). Cocultures were incubated for 48 hours, and % dead CD34⁺ cells were determined by flow cytometry as described in “Materials and methods.” (B) PBMCs exposed, or not, to live HSV-1 were added to primary AML cells, and % dead CD34⁺ cells were determined after 48 hours as above. *P < .005 from PBMCs alone. (C) CD56-, CD4-, and CD8-positive cells were purified from 2 healthy donors by EasySep methodology as described in “Materials and methods.” Isolated cells were then exposed, or not, to UV-HSV-1 (0.1 pfu/PBMC) for 16 hours and tested for their cytolytic activity against OCI-AML3 cells, and the results are expressed as killed OCI-AML3 cells per 1000 effector lymphocytes. **P < .001 from CD4 or CD8, UV-HSV-1–exposed lymphocytes. (D-E) Healthy PBMCs were exposed, or not, to UV-HSV-1 as above, and their cytolytic activity (30:1 effector to target ratio) against OCI-AML3 or healthy allogeneic lymphocytes (from the other donor tested in each graph) was determined as described in “Materials and methods.” *P < .0001 from unexposed PBMCs.