Differentiation of lymphatics from blood vessels in the broad ligament of the swine using S-100 protein immunohistochemical localization in the vascular endothelium.

We examined the immunohistochemical staining characteristics of S-100 protein in the vessels of the broad ligament of the swine uterus. The endothelial cells of arterial vessels, lymphatics and blood capillaries as well as nerve fiber bundles showed S-100 protein positivity. In contrast, the endothelial cells of veins did not react for the S-100 antiserum. Immunoreactivity for S-100 protein in the endothelial cells of lymphatics did not consistently demonstrate strong staining intensity. Accordingly, we filled lymphatics with colored gelatin before immunohistochemical staining to facilitate identification of lymphatics under light microscopy. Numerous arterioles and capillaries (of which the endothelial cells were immunopositive for S-100 protein) in the lymphatic walls, especially those in the paraovarian vascular plexus, support the existence of a microvascular arterio-arterial rete mirabile network.