Naive T cells:

CD4 and CD8 T cells leave the thymus and enter circulation as resting cells in the G0 stage of the cell cycle. These naive cells express high levels of the homing receptor L selectin which allows them to bind to a vascular addressin that is present only on high endothelial venules (HEVs) of the . Naive T lymphocytes travel to T-cell areas of secondary lymphoid organs in search of antigen presented by DCs.

Naive T lymphocytes continuosly circulate through the lymphatic system and the blood. They enter LN from the blood stream at high endothelial venules, migrate through the T cell areas of the cortex to the cortical sinus and, if not activated, leave the LN via the efferent lymph a few hours after entry.

When blood-borne naive T cells home to lymph nodes, they first roll on high endothelial venules using CD62L. This allows the chemokine receptor CCR7 to engage its ligand SLC, which is displayed by endothelial cells. The CCR7-SLC interaction activates integrins that promote firm adhesion and transmigration of the T cells into the lymph node.

When naive CD4+ T cells recognize their antigen on interdigitating DC in the T cell areas, they remain in the LN and proliferation in the paracortex. At day 2 after the initial stimulation, many primed T cells start to move to the borders of the B cell follicles and interact with antigen-specific B cells. Subsequently, activated CD4+ T cells either enter the follicles and participate in the germinal center reaction or leave the LN.

Effector T cells: are able to migrate into non-lymphoid tissues. Effector cells down regulate CCR7 and CD62L. They up regulate CCR5 and CCR2.

A fraction of primed T lymphocytes persists as circulating memory cells that can confer protections and give, upon secondary challenge, a qualitatively different and quantitatively enhanced response.