Pulmonary inflammation and immune responses during the course of Nippostrongylus brasiliensis infection: lymphocyte subsets in bronchoalveolar lavage fluids of rats.

Quantitative measurements were made of different phenotypes of lymphocytes in bronchoalveolar lavage fluid (BALF) of rats during the course of a primary or secondary infection with Nippostrongylus brasiliensis. These changes were compared with those in the peripheral blood to understand the site-specificity of the responses. Following infection, there was a significant increase in both B and T lymphocytes in BALF. The CD4:CD8 ratio was significantly altered with a decreased ratio on day 2 and increased ratio on days 16 and 32 post infection (p.i.). Two colour analysis showed that during larval migration through the lungs (day 2 p.i.) there was a significant increase in CD8+, CD4+ OX22+ and CD4+ OX22- cells in BALF. As infection progressed in time, CD4+ OX22- cells were increased significantly. Compared to primary infection, a secondary infection resulted in increased recovery of CD4+ OX22- cells in BALF. These changes were not readily appreciated in the peripheral blood, suggesting site-specific compartmentalization of lymphocyte responses in the lung. The functional significance of these dynamic changes in lymphocyte subsets in the airspaces following infection remains to be identified.