A, supernatants from 293S cells transfected with the same amount of the indicated constructs were captured by goat anti-human IgG and detected in enzyme-linked immunosorbent assay with mAb CBR IC1/11. B, purified ICAM-1_Fc preparations (1 μg/ml) were captured as described in A and subjected to enzyme-linked immunosorbent assay with mAbs RR1/1, CBR IC1/11, CBR IC1/12, and CA-7. Results are presented as the percentage of binding to wild-type ICAM-1_Fc. C, inhibition by soluble, monomeric ectodomain fragments of Hi3 or wild-type ICAM-1 of binding of soluble, multim-eric ICAM-1/IgA-Fc to αLβ2 on K562 cells in the presence of 1 mm Mn2+ D, inhibition by soluble Hi3 or wild-type ICAM-1 D1–D5 of binding of phorbol 12-myristate 13-acetate-stimulated peripheral blood lymphocytes to immobilized wild-type ICAM-1 in the presence of 5 mm Mg2+ Results are mean ± S.D. of multiple experiments (n = 2– 4)