Killing of granulocytes by autologous cytotoxic cells of patients with PNH. (A) 2-color flow cytometry showed that both CD56⁺ and CD8⁺ cells expressed NKG2D in a representative patient with PNH (patient no. 1 in Table 1) and a healthy volunteer. Dotted lines show nonspecific background staining with isotype-matched control Ig. The percentages of cells in each quadrant are indicated. (B-C) Killing of granulocytes (○) and K562 cells (•) was assessed by 4-hour cytotoxicity assay with autologous PBMCs. (B) Representative of 4 healthy donors. (C) Left panel, representative of 3 PNH patients not having granulocytes with membrane ULBPs; middle and right panels, representatives of 5 patients with PNH having granulocytes with membrane ULBPs. Only the patients with ULBP⁺ cells also had MICA⁺ cells, whereas the patients without ULBP⁺ cells did not. E/T ratio indicates NK cells in PBMCs-target cells (K562 cells or isolated granulocytes).