NKG2D Signaling Leads to NK Cell Mediated Lysis of Childhood AML

Figure 4

NKG2D ligand expression of the primary childhood AML blasts, AML-2 and AML-9, and the erythroblastoid cell line K562. Cells were incubated with unlabeled mouse anti-human ULBP1 and ULBP2 antibody and incubated in a second step with a PE labelled secondary goat anti-mouse antibody and measured on a FACSCalibur flow cytometer. Isotype control corresponds to the black line; the ULBP1 and ULBP2 positivity of the cells is displayed in shaded grey. In AML-2, 51.34% of the cells were ULBP1 positive and 49.40% were ULBP2 positive. In AML-9, 95.74% of the cells were ULBP1 positive and 95.12% were ULBP2 positive. In K562, 91.34% were ULBP1 positive and 86.14% were ULBP2 positive. The percentage of positive ULBP1 and ULBP2 cells was obtained by histogram subtraction method. The Median Fluorescence Intensity Ratio (MFIR) for AML-2 was 2.82 for ULBP1 and 3.34 for ULBP2; for AML-9, it was 117.67 for ULBP1 and 28.35 for ULBP2; for K562, it was 19.28 for ULBP1 and 15.35 for ULBP2. MFIR was calculated by the MFI goat anti-mouse PE divided by the MFI isotype control.