Do all the lymphocytes (whether activated or not) pass from the blood through the High Endothelial Venules to the lymph?
A No. Naive lymphocytes constantly recirculate from the blood to the lymph. it allows T cells of rare specificities to ‘sample’ Ag presented by dendritic cells in lymph nodes. Activated T cells will then migrate to inflammatory sites, while unstimulated T cells remain naive and recirculate. Memory lymphocytes may be in lymphtic or other tissues. Some memory T cells, like naive T cells, express L-selectin, and thus may pass into LN through HEV.
