Opposite effects of anti-CD44 MoAbs J173 and H90 on spontaneous adhesion of CD34⁺ cells to immobilized HA. ⁵¹Cr-labeled CD34⁺ cells (2 × 10⁵ cells/mL) were incubated at 4°C for 15 minutes with 5 μg/mL of IgG1, J173, or H90 MoAbs in the cell adhesion medium and put in contact for 15 minutes at 37°C with immobilized HA in 96-well culture plate (100 μL per well, 3 wells per point). After discarding the nonadherent cells by two washes, the adherent cell-associated radioactivity was measured using a β scintillator counter as described in the Materials and Methods. Data, expressed as the percentage of the radioactivity of the input, are the means ± 1 SE calculated from five independent experiments.