TF activation by ATG is dependent on complement activation and C5b-7 membrane insertion. (A) IgG- or ATG-loaded THP1 cells were mixed 1:1 (v:v) with PBS, NHP, or heat-inactivated NHP for 5 minutes at 37°C. Following washes, cell-associated FXa generation was measured using a chromogenic end point assay in the presence or absence of inhibitory anti-TF. Results are expressed as fold increase over IgG-loaded cells mixed with PBS (mean ± SD, n = 3). (B) ATG-loaded THP1 cells were exposed to NHP in the presence of increasing concentrations (31.25-500 µM) of compstatin. Results are expressed as percent PCA of ATG-loaded cells exposed to NHP in the absence of compstatin. A representative experiment is shown. (C) Inhibition of ATG-mediated TF activation on THP1 cells by C5 monoclonal antibody eculizumab (mean ± SD, n = 3). (D) ATG-loaded THP1 cells were exposed to normal or C7- or C8-deficient serum. Following washes, cell-associated FXa generation was measured as described above. Results are presented as percent FXa generation of ATG-loaded cells exposed to normal human serum. A representative experiment is shown. (E) Inhibition of ATG-mediated TF activation on THP1 cells by C7 monoclonal antibody (mean ± SD, n = 3). (F) Effect of C9 monoclonal antibody X (also see Materials, Antibodies section)197 (αC9) on ATG-mediated (left) TF activation and (right) PI uptake. The antibody was used at 50 µg/mL (mean ± SD, n = 3-6).