Preferential migration of effector CD8⁺ T cells into the interstitium of the normal lung

The respiratory tract is a primary site of infection and exposure to environmental antigens and an important site of memory T cell localization. We analyzed the migration and retention of naive and activated CD8⁺ T cells within the noninflamed lungs and quantitated the partitioning of adoptively transferred T cells between the pulmonary vascular and interstitial compartments. Activated but not naive T cells were retained within the lungs for a prolonged period. Effector CD8⁺ T cells preferentially egressed from the pulmonary vascular compartment into the noninflamed pulmonary interstitium. T cell retention within the lung vasculature was leukocyte function antigen-1 dependent, while the egress of effector T cells from the vascular to the interstitium functions through a pertussis toxin-sensitive (PTX-sensitive) mechanism driven in part by constitutive CC chemokine ligand 5 expression in the lungs. These results document a novel mechanism of adhesion receptor- and pulmonary chemokine-dependent regulation of the migration of activated CD8⁺ T cells into an important nonlymphoid peripheral site (i.e., the normal/noninflamed lung).