Mice Lacking Expression of Secondary Lymphoid Organ Chemokine Have Defects in Lymphocyte Homing and Dendritic Cell Localization

Gunn, Michael D.; Kyuwa, Shigeru; Tam, Carmen; Kakiuchi, Terutaka; Matsuzawa, Akio; Williams, Lewis T.; Nakano, Hideki

DCs are distributed throughout the body at sites where they can capture antigens (9) . In response to an inflammatory stimulus, these cells migrate into afferent lymphatics, then are carried to draining LNs where they are deposited in the subcapsular space. From the subcapsular space, DCs migrate into T cell zones where they take up residence as interdigitating DCs and present MHC-bound antigens and costimulatory molecules to passing lymphocytes (10) (11) (12) (13) (14) (15) . To sample this antigen repertoire, T lymphocytes that have never been stimulated by antigen (naive T cells) migrate or "home" specifically to the T cell zones of secondary lymphoid organs. In LNs and Peyer's patches (PPs), lymphocytes leave the blood through specialized high endothelial venules (HEVs) by a series of discrete steps which include selectin-mediated rolling, integrin activation, integrinmediated firm adhesion, and endothelial extravasation (16, 17) . In spleen, which lacks HEVs, lymphocytes exit the blood in the marginal zone and migrate to the T cell zone within the splenic white pulp by a poorly understood route (18) . Within the T cell zones of these lymphoid organs, a 452 Leukocyte Trafficking in Mice Lacking SLC continuous flow of naive T cells sample the antigens presented by DCs. Most of these lymphocytes eventually return to the circulation. The few that encounter their cognate antigen are retained within the T cell zone, undergo clonal expansion, and differentiate into effector or memory T cells.