Migration of intramediastinally injected thymocytes in draining nodes

The present study investigated the migration, in the lymph node, of cells entering the organ via the subcapsular sinus. Thymocytes of rats were labelled with 3H-thymidine and injected into the mediastinal cavity of syngeneic recipients. These animals were sacrificed at various intervals after injection. Five minutes after injection, labelled cells were found in the subcapsular sinus, and even in the peripheral cortex, of the draining mediastinal lymph nodes. The overall of the radioautographic observations reveals a migration of cells from the peripheral cortex towards the deep cortex, and into the medullary cords. The observations indicate that such migration can occur in less than 12 hours. Nevertheless, six hours after the injection, some labelled cells had escaped already the draining nodes and migrated into the other lymphoid organs. It is a fact that some of our results suggest that cells may pass directly from the subcapsular into the medullary sinuses without previously migrating into the nodal parenchyma. As to folliculo-nodules and pseudo-follicles, they exhibited relatively few labelled cells. Moreover, some of our findings indicated that cell migration was much slower in the pseudo-follicles than in the extrafollicular zone.