Isolated primary mouse HPCs express encrypted TF on the cell surface. Primary HPCs were isolated from control mice (TF^flox/flox mice). (A) Intact HPCs were incubated with various concentrations of inhibitory rat anti-mouse TF antibody (clone 1H1, 10-100 μg/mL) or isotype control antibody (clone 54447) for 15 min prior to determination of FXa generation. (B) Intact HPCs were incubated with rat anti-mouse TF antibody (clone 1H1, 100 μg/mL) for 15 min, the unbound antibody was removed by washing, and FXa generation by intact and detergent-lysed (see Methods) HPCs was determined. (C) Intact HPCs were incubated with 15 mM sulfo-NHS-SS-biotin for 15 min, excess reagent removed by washing, and FXa generation by intact and detergent-lysed (see Methods) HPCs was determined. FXa generation by HPCs was assessed in the absence of exogenous FVIIa (see Methods). FXa levels are expressed as mean + SEM (pM/min) from 3 independent experiments. For panel A, *significantly different from respective isotype control group. For panels B-C,* significantly different from respective treatment without lysis. ^#Significantly different from respective group without TF inhibitor (P < .05).