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

In pulmonary immune reactions the cells which can be obtained by bronchoalv eolar lavage (BAL) are only one part of the picture. In this study the kine tics of an experimental pulmonary immune response were investigated simulta neously 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, leuk ocytes were taken from the bronchoalveolar, the interstitial and the margin al lung vascular pool as well as from the peripheral blood. Total numbers o f granulocytes, NK cells, B and T cells, CD4(+) and CD8(+) cells were deter mined. 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 o f CD4(+) T cells. Changes in the lung interstitium showed a similar tendenc y, but were not found in the marginal pool or blood. Histologically cellula r infiltrates were seen around the pulmonary small vessels. Little local pr oliferation occurred in the different lung compartments, indicating mainly immigration of cells. Further studies will focus on the expression of adhes ion molecules during an immune response, to learn more about the mechanisms responsible for the increase of lymphocytes.