Cytotoxicity assay with various inhibitors.

The killing of target cells by NK cells was perforin-mediated. Cytolysis by peripheral NK cells of K562 cells with (▪) and without (■) PIG-A mutation in the presence of a calcium chelate EGTA (A) and concanamycin A (B). E/T ratio was 64:1. Each value represents the mean (± SD) of triplicate assays.