γδ T cells regulate the early inflammatory response to Bordetella pertussis infection in the murine respiratory tract

The role of 78 T cells in the regulation of pulmonary inflammation following Bordetella pertussis infection was investigated. Using a well-characterized murine aerosol challenge model, inflammatory events in mice with targeted disruption of the T-cell receptor delta-chain gene (gamma delta TCR-/- mice) were compared with those in wild-type animals. Early following challenge with B. pertussis, gamma delta TCR-/- mice exhibited greater pulmonary inflammation, as measured by intra-alveolar albumin leakage and lesion histomorphometry, yet had lower contemporaneous bacterial lung loads. The larger numbers of neutrophils and macrophages and the greater concentration of the neutrophil marker myeloperoxidase in bronchoalveolar lavage fluid from gamma delta TCR-/- mice at this time suggested that differences in lung injury were mediated through increased leukocyte trafficking into infected alveoli. Furthermore, flow cytometric analysis found the pattern of recruitment of natural killer (NK) and NK receptor(+) T cells into airspaces differed between the two mouse types over the same time period. Taken together, these findings suggest a regulatory influence for gamma delta T cells over the early pulmonary inflammatory response to bacterial infection. The absence of 76 T cells also influenced the subsequent adaptive immune response to specific bacterial components, as evidenced by a shift from a Th1 to a Th2 type response against the B. pertussis virulence factor filamentous hemagglutinin in gamma delta TCR-/- mice. The findings are relevant to the study of conditions such as neonatal B. pertussis infection and acute respiratory distress syndrome where gamma delta T cell dysfunction has been implicated in the inflammatory process.