Correlation of perforin binding and subsequent cell death of K562 and ML-2 cells.

The cells were incubated for 4 hours with 100 μg total protein of the NK lysates, 0.02% NP-40, or 10 U/mL complement. After staining dead cells with PI and perforin on the cell surface with a FITC-labeled perforin antibody, cells were analyzed in FL1 (FITC) versus FL2 (PI) dot plots by flow cytometry. (A) K562 cells + NK lysates, (B) ML-2 cells + NK lysates, (C) K562 cells + 10 U/mL complement, and (D) K562 cells + 0.02% NP-40.