Effect of CD157 on the adhesion of neutrophils to fibrinogen. (A) ⁵¹Cr-labeled neutrophils were plated in fibrinogen-coated wells (in triplicate samples) in the presence of 10 μg/mL anti-CD157, anti-CD18, or anti-HLA class I mAbs and incubated at 37°C for increasing amounts of time. (B) ⁵¹Cr-labeled neutrophils were plated in fibrinogen-coated wells in the presence of increasing concentrations of anti-CD157 or anti-CD18 mAbs and incubated for 1 hour at 37°C. After washing, adherent neutrophils were lysed with 2% Triton X-100 (100 μL) and the released radioactivity was quantified in a γ-counter. Percent inhibition of adherence was calculated using the following formula: [(cpm in the presence of control IgG - cpm in the presence of relevant mAb / cpm in the presence of control IgG) × 100]. Results represent the mean ± SD of 3 independent experiments. (C) ⁵¹Cr-labeled PMNs from healthy donors (▦) or patients with PNH (▪) were plated in fibrinogen-coated wells (in triplicate samples) and incubated at 37°C for increasing time. After washing to remove nonadherent cells, adherent PMNs were lysed with 2% Triton X-100 (100 μL) and the released radioactivity was quantified in a γ-counter. Percent specific adhesion was calculated using the following formula: [(⁵¹Cr released from adherent cells / total ⁵¹Cr added to each well) × 100]. Results represent the mean ± SD of 3 independent experiments. ^*P < .05.