The Liver Lymphatics as a Migratory Pathway of Macrophages from the Sinusoids to the Celiac Lymph Nodes in the Rat

A migratory pathway of macrophages as well as lymphatic communications from the liver to the celiac lymph nodes were studied both macroscopically and histologically. The injection of gelatinized carbon into the porta hepatis revealed a new pathway of the liver lymphatics running independently of the portal vein in addition to the ordinary periportal lymphatics. By obstruction of the efferent lymph flow of the celiac nodes and immunostaining with a monoclonal antibody to lymphatics, perilobular lymphatic vessels in the portal tract was readily demonstrated. It was suggested that heavily carbon-laden (HC) macrophages had migrated from the sinusoid into the interlobular connective tissue by 6h after an intravenous injection of carbon, and then entered the lymphatic vessels of the portal tract. By 9h to 12h after carbon injection, HC macrophages started to migrate into the celiac nodes via the two lymphatic pathways. From the marginal sinus in the celiac nodes, they moved into the inter-follicular area of the superficial cortex, then accumulated in the paracortex by 12h to 24h. They finally ended up in the corticomedullary junction. Migrating HC macrophages showed morphological homogeneity. The liver lymphatic pathway in the rat and a significance for the translocation and function of migrating macrophages were discussed.