Memory also requires that lymphocytes demonstrate a complex migratory pattern called homing. Thus, lymphocytes pass from the circulation into various tissues, from which they subsequently depart, and then pass by way of lymphatics to reenter the circulation. Homing involves the dynamic interaction between lymphocytes and endothelial cells using multiple cell-adhesion molecules. Usually the major types of lymphocytes that migrate into tissue sites are memory lymphocytes that express higher levels of certain cell-adhesion molecules, such as the integrins, than do naive cells. In contrast, naive lymphocytes tend to migrate to lymphoid tissues, where they may meet their cognate antigen. Inflammation, however, changes the rules and breaks down homing patterns. At inflammatory sites, the volume of lymphocyte migration is far greater and selection much less precise, although migration of memory cells or activated lymphocytes still exceeds that of naive cells.
Excerpted from BCSC 2020-2021 series: Section 9 - Uveitis and Ocular Inflammation. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.