Lymphocyte migration.

Lymphocyte migration is strictly regulated by cell adhesion receptors on lymphocytes (lymphocyte homing receptors) and endothelium (vascular addressins). Naive lymphocytes migrate randomly through the body because they express both α₄β₇ (for mucosal homing) and L-selectin (for homing to peripheral lymph nodes). Migration of activated lymphocytes to sites of inflammation involves several receptor-ligand pairs, including selectin-sialomucin, α₄β₁-VCAM-1, α₄β₁-CS-1, and CD44-hyaluronate interactions. Homing of memory lymphocytes is largely restricted to organs of primary antigenic stimulation. By binding to their vascular addressins, lymphocyte homing receptors α₄β₇, L-selectin, and CLA mediate tissue-specific homing to the mucosa, peripheral lymph node, and skin, respectively. Interaction of αEβ₇ with E-cadherin A metastasisexpressed on epithelial cells is involved in positioning of lymphocytes in the epithelium of skin and mucosa. The NHLs related to lymphocyte populations with tissue-specific homing properties are shown in the boxes. These tumors usually display tissue-specific dissemination patterns and express homing receptors corresponding to the tissue of origin.