Lymphatic vessels were missed by many pathologists for centuries because they do not contain red blood cells. Yet the reason for this has been illuminated only now in several articles in Blood. The main function of the lymphatic vessels is to return excess tissue fluid to the blood circulation. Other functions include antigen monitoring via the sieving function of the lymph nodes, and dietary lipid transport in chylomicrons via the intestinal lymph vessels. For the lymphatic vascular system to operate efficiently, the lymphatic vessels must separate from the blood vessels during development and the connections with the blood vessel lumen remain unidirectional at the sites where lymph drains into blood at the subclavian veins. Prior to reports in this and other recent issues of Blood, the mechanisms behind this separation and the reason for the leakage of blood into lymphatic vessels in several mouse mutant models were unknown. Now, it seems that the mystery has largely been resolved. The new evidence does not indicate a role for circulating endothelial progenitor cells as first suspected, but instead uncovers an important function for platelets, which are recruited to prevent the entry of blood into lymphatic vessels.
展开▼
