MICA and MICB expression on K562, MDS1, and 721.221 cell lines and on CD34⁺ bone marrow cells from MDS patients. Flow cytometry histograms for MICA/MICB expression on K562 cells, 721.221 tumor cells, and MDS1 cells. Isotype control expression (dotted line) was compared with samples stained with an equal amount of anti-MICA or anti-MICB antibody (solid line). Histograms represent results from individual patients (UPN). SFI was calculated using the equation described in “Patients, materials, and methods,” and specific value is shown in the histograms. The determination of positive (+) or negative (-) was based on an SFI value of at least 1.5 (indicated in the upper right hand corner of the histograms).