ULBP and NCR ligand expression is low on CD34+ cells and well pronounced on myeloid progenitors in normal BM. ULBP expression was determined by FACS in the indicated BM subpopulations. (A) BM staining with ULBP1-specific mAbs (bold line) or control secondary FITC-labeled goat anti–mouse IgG alone (thin line). (B) BM staining (from 3 healthy donors) with mAbs to ULBP1, ULBP2, ULBP3 and to sNKp30, sNKp44, and sNKp46 dimers. ▪ indicates CD34+CD33-; ▦, CD34⁺CD33⁺; □, CD34^- CD33⁺CD14^-; and ▨, CD34^- CD33+CD14+ cell populations.