Vascular endothelial markers of the human thoracic duct and lacteal

Factor VIII-related antigen (F8) and Ulex europaeus lectin (UEL) are accepted markers for human blood vessel endothelium. However, disagreement exists as to whether lymphatic vessels stain for F8, and accordingly this study was undertaken to address this issue. Moreover, another vascular endothelial marker, angiotensin converting enzyme (ACE) was also examined in lymphatics. Segments of human thoracic duct and portions of small bowel containing lacteals with post-mortem intervals of less than 15 hours, were removed at autopsy and fixed in B5 or formalin. The specimens were processed routinely and sections examined by indirect immunohistochemical techniques for F8 (Dako Corp.), ACE and for UEL (EY Lab). F8, UEL, and ACE positivity was uniformly found in thoracic ducts and lacteals; however, the staining intensity was less in lymphatic vessels with F8 and UEL than with comparable arteries or veins. ACE staining intensity, on the other hand, was similar in blood vessels and lymphatics. Both formalin and B5 fixation preserved antigenicity; however, background staining was greater with B5 fixation whereas tissue staining was slightly more intense with formalin fixation.