Lymphocyte trafficking and the tissue-specific dissemination of T-cell lymphomas. Lymphocyte migration is strictly regulated by adhesion molecules and chemokine receptors on lymphocytes and their ligands expressed by the endothelium. Naive T lymphocytes can home and recirculate via all secondary lymphoid tissues because they express both α4β7 (for mucosal homing) and L-selectin (for homing to peripheral lymph nodes). Migration of activated T lymphocytes to sites of inflammation involves several receptor-ligand pairs, including selectin-sialomucin, α4β1-VCAM-1, α4β1-CS-1, and CD44-hyaluronate interactions. Upon antigen priming by dendritic cells, T lymphocytes become memory cells and acquire a “homing signature,” that is, a specific adhesion and chemokine receptor make-up, which enables them to selectively home to specific tissue environments, thereby increasing the efficacy of immunosurveillance. The T-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.