While both the spleen and lymph nodes are called secondary lymphoid tissues, how lymphocytes enter these tissues are quite different from each other. This is because the architecture of the two types of organs and the mode of lymphocyte migration into these organs are quite distinct. In the spleen, T cells are passively released in the blood flow from the arterioles in the red pulp and marginal zone area. In contrast, T cells in the blood are actively captured on high endothelial venules in lymph nodes by the coordinated actions of CCR7 and several adhesion molecules. A recent finding indicates that T cells, released in the red pulp and marginal zone areas, actively find their way to the white zone by utilizing the migration track created by periarteriolar stromal cells. This finding adds one more piece to our understanding of lymphocyte migration for effective adaptive immune responses in the spleen.

虽然脾脏和淋巴结都被称为继发性淋巴组织，但淋巴细胞如何进入这些组织却彼此截然不同。这是因为两种器官的结构和淋巴细胞迁移到这些器官的方式非常不同。在脾脏中，T细胞在血流中从红髓和边缘区的小动脉被动释放。相反，血液中的T细胞通过CCR7和几种粘附分子的协同作用被主动捕获在淋巴结的高内皮小静脉上。最近的发现表明，在红髓和边缘区域释放的T细胞通过利用小动脉周围基质细胞产生的迁移轨迹，主动找到了通往白色区域的途径。