Anatomy of a pulmonary immune response: Kinetics in different leukocyte pools

Abstract

In pulmonary immune reactions the cells which can be obtained by bronchoalveolar lavage (BAL) are only one part of the picture. In this study the kinetics of an experimental pulmonary immune response were investigated simultaneously in different lung compartments in the same rat. On days 0, 1, 2, 3, 4, 5 and 11 after intratracheal challenge with sheep red blood cells, leukocytes were taken from the bronchoalveolar, the interstitial and the marginal lung vascular pool as well as from the peripheral blood. Total numbers of granulocytes, NK cells, B and T cells, CD4⁺ and CD8⁺ cells were determined. Histology and in vivo labeling of proliferating cells was performed. On day 1 after challenge an increase of granulocytes in the BAL was found. In the BAL the total number of T lymphocytes increased on day 1 and day 2 and the CD4/CD8 ratio increased from day 1 to day 5, indicating an influx of CD4⁺ T cells. Changes in the lung interstitium showed a similar tendency, but were not found in the marginal pool or blood. Histologically cellular infiltrates were seen around the pulmonary small vessels. Little local proliferation occurred in the different lung compartments, indicating mainly immigration of cells. Further studies will focus on the expression of adhesion molecules during an immune response, to learn more about the mechanisms responsible for the increase of lymphocytes.