Analysis of MBB2 binding to purified β2GPI. (A) Human or mouse β2GPI (10 μg/mL) immobilized on γ-irradiated polystyrene plates was incubated with different concentrations of MBB2 or control minibody (MB) for 90 minutes at room temperature, and the bound scFv-Fc was measured by ELISA. (B) Binding of MBB2 to human β2GPI domains (10 μg/mL). (C-D) Binding of MBB2 or control MB to HUVECs or BeWo cells grown to confluence in 96-well tissue culture plates. The cells were incubated with β2GPI (5 μg/mL) or 20% FCS prior to exposure to the scFv-Fc, and the bound antibodies were measured using ELISA. The data were analyzed with the Mann-Whitney test. The results are expressed as mean ± SD of 3 different experiments performed in triplicate. *P < .05 vs control MB.