Figure 3. Monocytes are the major cellular source for endothelial TF activity. PBMC and monocyte-depleted PBMC (Mo-depleted) preparations (10⁶/mL) in triplicate were challenged with live S. mutans, S. oralis, and S. sanguinis 10556 at 10⁷/mL for 4 hrs. The supernatant fluids were harvested and assayed for their induction of endothelial TF activity (factor Xa). Data were analyzed with two-way ANOVA, and the differences between PBMC and Mo-depleted preparations for each strain were examined with post hoc comparisons. This experiment was repeated with another donor with a similar pattern. *Significantly lower factor Xa titer than its respective PBMC control (p < 0.0002). The vertical bars represent standard deviations.