This binding is transient, as the shear of the blood flow detaches the neutrophil. The neutrophil then binds and detaches from selectins on subsequent endothelial cells. Lymphocytes enter secondary lymphoid tissues by binding to adhesion molecules on high endothelial venules and passing across the vessel wall. See Kuby Figure 15-4. The homing of specific lymphocytes to specific sites is influenced by which adhesion molecules are expressed in the lymphoid tissue and on the lymphocyte.
Naive lymphocytes circulate throughout the body.
They recirculate constantly through secondary lymphoid tissues in search of antigen. If they encounter antigen, they stay in the lymphoid tissue and initiate a specific immune response. If they do not encounter antigen, they leave the lymphoid tissue and continue recirculating throughout the body. After this, progeny of the original cell leave the lymphoid tissue and may recirculate. Memory cells home to the type of tissue in which they first encountered antigen.