Colocalization of anti-TFPI antibodies with endosomes and lysosome marker proteins on cryosections of HUVEC. (A) Cell labeled with anti-mannose-6-phosphate receptor (MPR, small gold), considered to be a marker for late endosomes. The anti-TFPI (large gold, arrowheads) labeling is present in MPR-positive structures. Bar = 0.2 μm. (B) Smaller, MPR-positive vesicles (small gold) also labeled with anti-TFPI (large gold). The anti-TFPI also labels the cell surface. Bar = 0.2 μm. (C) Cell labeled with anti-LAMP (small gold), which is found in late endosomes and lysosomes. The anti-TFPI (large gold, arrowheads) is present in LAMP 1-positive structures. Bar = 0.2 μm.