Thymic cell migration in the subnodular spaces of draining lymph nodes of rats

Little is known about the pathway of possible lymphocyte traffic in the nodules (germinal centers) of the node. Observations reported here indicate the involvement of the subnodular spaces. These spaces, which constitute the inner limit of the nodules, are contiguous to the perivascular channels of the postcapillary venules which partially encircle each nodule. Twelve hours after a local transfer of labeled thymic cells, they were observed in the subnodular spaces and in the perivascular channels of the draining nodes. It is proposed that the spaces and the channels provide a pathway for the rapid migration of lymphocytes entering a node via the afferent lymph and, probably, carrying an immunogenic information. The pathway would permit these cells to transmit the information rapidly to the appropriate cell population(s) of a node draining a tissue undergoing an immunological process.