The CD164 mucin-like glycoprotein functions as an adhesion molecule expressed by CD34⁺ and BM stromal cells. Allogeneic BM stromal cells (2 × 10⁴) were transferred to each well of a 96-well plate 24 hours before performing the assay. BM CD34⁺ cells isolated with 561-Dynabeads were labeled with ⁵¹Cr and subsequently incubated on ice at 1 × 10⁵/mL in RPMI (supplemented with 2% FCS) containing 20 μg/mL of the MoAb 105.A5, 103B2/9E10, IgM, and IgG3 nonbinding control MoAbs, or the anti-VLA4 (P4C2) and VLA-5 MoAbs (PHM2), as indicated. Cells (1 × 10⁴ in a volume of 100 μL) were subsequently transferred (without washing) to each well of the 96-well plate containing stromal cells. Incubation was performed for 30 minutes at 37°C, after which unbound cells were removed by washing. Adhesion was quantitated by liquid scintillation counting of solubilized lysates. Data are presented as the percentage of control adhesion obtained in the presence of a cocktail of IgG₃ and IgM nonbinding control MoAbs and represents the mean ± SE of three experiments.