LYMPHOCYTE SUBSETS IN DISTINCT LUNG COMPARTMENTS SHOW A DIFFERENT ABILITY TO PRODUCE INTERFERON-GAMMA (IFN-GAMMA) DURING A PULMONARY IMMUNE-RESPONSE

Lymphocytes play an important immunoregulatory role in pulmonary immun e responses. By releasing cytokines they can control the cell-cell com munication of other participating cells. Although it is well establish ed that the lung lymphocytes, localized in distinct compartments, diff er in their subset composition, little is known about cytokine product ion in these compartments during immune responses. Lewis rats were imm unized by intravenous administration of sheep erythrocytes on day 0 an d day 7 and challenged intratracheally with sheep erythrocytes on day 10. Four days after intratracheal (i.t.) challenge the composition of lymphocyte subsets (CD2(+), CD4(+): CD8(+), B cells: natural killer (N K) cells) in the spleen, blood, lung perfusate. lung tissue and bronch oalveolar lavage fluid (BALF) was characterized, and intracellular IFN -gamma was detected in these subsets by flow cytometry. Comparing cont rol and immunized animals, no changes were found in lymphocyte numbers , subsets or the percentage of IFN-gamma-producing lymphocytes in the spleen, blood and lung perfusate. In lung tissue and BALF, however, th e absolute number of all lymphocyte subsets and the percentage of IFN- gamma-producing lymphocytes were increased. When the lymphocyte subset s were analysed an increased percentage of IFN-gamma-producing T cells was found in lung tissue (4.5 +/- 0.6% versus 12.8 +/- 1.1%) and in B ALF (7.8 +/- 1.4% versus 14.8 +/- 1.9%) of immunized animals opposed t o controls, this increase being seen in both CD4(+) and CD8(+) cells. Thus, there is an accumulation of T cells with an increased potential to produce IFN-gamma in the lung interstitium and the bronchoalveolar space during pulmonary immune responses.