Increase of gamma delta T lymphocytes in murine lungs occurs during recovery from pulmonary infection by Nocardia asteroides

Previous studies have demonstrated that gamma delta T lymphocytes are impor tant for host resistance to pulmonary infection of the murine lung by log-p hase cells of Nocardia asteroides. To study the role of gamma delta T cells in nocardial interactions in the murine lung, C57BL/6J wild type and C57BL /6J-Tcrd (gamma delta T-cell knockout mice) were infected intranasally with log-phase cells of N. asteroides GUH-2. At 3, 5, and 7 days after infectio n, the gamma delta T cells were quantified by multiparameter flow cytometry . At the same time, Gram and hematoxylin-eosin stains of paraffin sections were performed to monitor the host responses. The data showed that gamma de lta T lymphocytes increased significantly within the lungs after intranasal infection, and the peak of this cellular increase occurred at 5 days. Furt hermore, at this time, greater than 50% of the CD3 T-cell receptor (TCR)-po sitive (CD3(+)) cells were gamma delta TCR positive. Histological examinati on clearly showed divergent inflammatory responses in the lungs of wild-typ e mice compared to gamma delta T-cell knockout mice. The C57BL/6J-Tcrd mice were less capable of clearing the organism, and the polymorphonuclear leuk ocyte response lasted longer than in wild-type C57BL/6J mice. These results showed that gamma delta T cells were actively involved in modulating the i nnate host responses to murine pulmonary infection by N. asteroides.