Blood‐to‐lymph migration of small lymphocytes through the liver of the sheep

The process of lymphocyte migration is required for the systemic dissemination of immunological memory and immune surveillance. We report here experiments to quantitate the normal traffic of lymphocytes that occurs from blood to lymph through the liver and hepatic node in the sheep. Comparisons were made with known lymphocyte homing pools. Individual afferent hepatic lymphatics had cell outputs of 1.4 ± 0.1×106 cells/hr, suggesting that the total combined lymphocyte output from the liver was no greater than about 1×107 cells/hr. The lymphocyte output in efferent hepatic lymph was 6.2 ± 0.4×107 cells/hr, comparable to the cell outputs recorded from other lymph nodes of similar size. When the specificity of lymphocytes homing through the liver or hepatic node was examined, we found similarities to both the peripheral lymph node and intestinal lymph node homing patterns. Migration into afferent hepatic lymph was found to be different from that into intestinal or subcutaneous efferent lymph, and the kinetics of migration into hepatic afferent lymph was faster than that observed into efferent compartments. Intravenously injected endotoxin was found to alter the normal lymph flow through the liver tissue and the hepatic node; it appeared to enhance the migration of macrophages out of the liver by way of the afferent lymph. These studies suggest unique features of lymphocyte traffic through the liver and the need for further experiments on hepatic lymphocyte traffic, particularly in pathological states with substantial mononuclear cell infiltration. (Hepatology 1994;19:758–763).