Human hematopoietic and nonhematopoietic cell lines adhere to mouse or human ICAM-4 with similar avidity.

Adhesion to mouse and human ICAM-4 is mediated by α₄β₁ integrin on hematopoietic cells and by α_V integrins on nonhematopoietic cells. (A) Adhesion of Mn²⁺-activated HEL cells to mouse (m) or human (h) ICAM-4–Fc or NCAM-Fc control protein. The results are the percentage of total input cells bound ±SD (n = 3). Dilution analysis was performed and the concentrations of protein applied to microplate wells are indicated as abscissa. (B) Adhesion of Mn²⁺-activated HEL cells to mouse or human ICAM-4–Fc or NCAM-Fc control protein in the presence of function-blocking antibodies against integrin α or β subunits. The fusion proteins were applied at a concentration of 10 μg/mL. Results are shown as the percentage of total input cells bound relative to binding to control antibody ±SD (n = 6). Adhesion in the presence of mouse IgG1 (C1) or rat IgG (C2) control antibodies is shown as 100% (actual values obtained were in the range of 42%-50% or 55%-60% adhesion of input cells to human or mouse ICAM-4–Fc, respectively). Percent adhesion in the presence of mouse antibodies against α₂, α₄, α₅ or β₃, or rat antibodies against β₁ or α_V subunits is shown. N indicates percent adhesion to NCAM-Fc control protein in the absence of antibody. (C) Adhesion of PMA+Mn²⁺-activated FLY cells to mouse (m) or human (h) ICAM-4–Fc or NCAM-Fc control protein. The results are the percentage of total input cells bound ±SD (n = 3). Concentrations of protein applied to microplate wells are indicated as abscissa. (D) Adhesion of PMA+Mn²⁺-activated FLY cells to mouse or human ICAM-4–Fc or NCAM-Fc control protein in the presence of function-blocking antibodies against integrin α or β subunits. Fusion proteins were applied at a concentration of 10 μg/mL. Results are shown as the percentage of total input cells bound relative to binding to control antibody ±SD (n = 6). Adhesion in the presence of mouse IgG1 (C1) or rat IgG (C2) control antibodies is shown as 100% (actual values obtained were in the range of 65%-75% or 76%-80% adhesion of input cells to human or mouse ICAM-4–Fc, respectively). Percent adhesion in the presence of mouse antibodies against α_Vβ₅ integrin complex, α₄subunit or rat antibodies against β₁, α_V, or α₆ subunits is shown. N indicates percent adhesion to NCAM-Fc control protein in the absence of antibody.