Induction of TF by APS and WAHA ICs. (A) Induction of TF by β2GP1 α-β2GP1 ICs. THP-1 cells were incubated for 3 hours with ICs formed between β2GP1 and IgG rabbit α-β2GP1 antibody (Ab) in the absence or presence of α−FcRn Ab or with αβ2GP1 Ab alone. TF activity was determined as in Figure 1A. Data (mean ± standard error of the mean [SEM]) from 4 independent experiments is shown. ***P < .0001 by 1-way ANOVA with Sidak’s multiple comparison test. (B) Induction of TF by IgG-coated RBCs and inhibition by α-FcRn Ab. Rh(D)⁺ or Rh(D)⁻ RBCs were incubated with 100 ng/mL of mAb α-D IgG (BRAD-3) or α-D IgM (MAD-2). The RBCs were washed and added to THP-1 cells for 3 hours in the absence or presence of 200 µg/mL of α−FcRn Ab or an IgG4 control (Cont), and TF activity was measured as described in Figure 1A. Results from 2 to 5 independent experiments are shown (mean ± SEM). ***P < .0001, §P = .0003, and ¶P < .427 by 1-way ANOVA with Fisher’s least significant difference test.