Cell surface tPA-dependent plasmin generation in VTE. (A) PBMC-related plasmin generating capacity. PBMCs from HCs and subjects with history of VTE were incubated with human Glu-plasminogen, washed, and then incubated with tPA (Genentech) in the presence of the fluorogenic plasmin substrate AFC-81. Shown are individual RFU/min² values as well as means ± SEM for 60 HCs, 106 subjects with history of VTE, and VTE subgroups, including VTE with positive FH (VTE+FH, n = 45), VTE-FH (n = 61), VTE+FH+IT (n = 21), and VTE+FH-IT (n = 24). P values were determined using 1-way ANOVA and Tukey’s post hoc test of significance. Asterisks (* and **) indicate statistical significance (by Tukey’s post hoc vs unpaired t test, respectively). (B) Annexin A2–specific cell surface plasmin generation. HC PBMCs were incubated with Glu-plasminogen, followed by tPA (Molecular Innovations) and AFC-81 in the absence or presence of blocking monoclonal anti-A2 IgG or control IgG. Shown are values for mean RFU/min² ± SEM from 3 separate experiments combined. The data were analyzed using 1-way ANOVA and Tukey’s post hoc test of significance. (C) Stratification of cell surface plasmin generation values. Values for cell surface plasmin generation (RFU/min²) depicted in panel A were stratified into 10th-percentile bins. The proportion of samples from each group falling into the lowest decile is indicated above each bar and by the black solid bars. NS, not significant; PN, plasmin.