Distinct migration patterns of naive and effector CD8 T cells in the spleen: correlation with CCR7 receptor expression and chemokine reactivity

Changes in the migration pattern of lymphocytes represent a key event in th e evolution of an immune response since they enable lymphocytes to gain acc ess to infected tissues. We studied the location of virus-specific CD8 T ce lls in various splenic compartments in response to infection with lymphocyt ic choriomeningitis virus (LCMV), either in situ or by adoptive cell transf ers using T cells from transgenic (tg) mice expressing an LCMV-specific TCR . Naive tg T cells were predominantly localized in the periarteriolar lymph oid sheath, where they proliferated extensively after virus infection. In c ontrast, in vivo activated effector T cells failed to enter white pulp area s and accumulated in the red pulp. The different homing patterns of naive a nd effector CD8 T cells in vivo correlated well with their CCR7 chemokine r eceptor expression and their reactivity to the secondary lymphoid tissue ch emokine (SLC). Thus, down-regulation of CCR7 expression on CD8 effector T c ells rendered them unresponsive to SLC, which controls T cell homing into w hite pulp of spleen and lymph nodes. Exclusion of CD8 effector T cells from these sites may represent an important mechanism to protect professional a ntigen-presenting cells from cytotoxic T cell attack and thus to prevent a premature decline of the immune response.