Ultrathin cryosections through a human venous thrombus.

TF within the thrombus was detected by on-section labeling using mAb anti-TF (hTF1) followed by goat antimouse IgG conjugated to 10-nm colloidal gold. (A) Electronmicroscopy shows TF⁺ cell fragments adjacent to the fibrin strands. (B) Closeup of the region in the boxed field: a clearly discernible bilayered cell membrane and organelle substructure are indicative of the cellular origin of the TF⁺ structures.