Bronchoalveolar lavage cell--lymphocyte interactions in normal nonsmokers and smokers. Analysis with a novel system

We investigated the ability of smoker and nonsmoker pulmonary alveolar macrophages (AM) to facilitate lymphocyte proliferative responses in a novel system allowing separation of lymphocyte and AM effects. Bronchoalveolar lavage cells (BLC) were obtained from 7 nonsmokers and 5 older smokers and cultured with purified peripheral blood lymphocytes (PL) and the mitogen phytohemagglutinin. Increasing amounts of BLC were added such that BLC/PL ratios were 1:100, 1:10, 1:2, 1:1 of either autologous or homologous PL. Lymphocyte proliferation was dose-related, increasing with 1:100 and 1:10 BLC/PL ratios, and decreasing to or below initial responses with 1:2 or 1:1 ratios. Depletion of T-lymphocytes from BLC demonstrated that these effects were mediated by AM. Phytohemagglutinin (PHA) dose-response curves of nonsmokers obtained using autologous or homologous PL were not different. When BLC from smokers were cultured with autologous PL, lymphocyte proliferative responses were less than those of similar cultures from nonsmokers. However, when similar smoker BLC were cultured with homologous PL from nonsmokers, proliferative responses were not different from those of nonsmokers. Peak proliferative responses of peripheral blood mononuclear cells were not different from maximal proliferative responses of PL-BLC cultures at any PHA dose. These data show that human AM provide dose-related help and suppression of mitogen-induced lymphocyte proliferation similar to that reported with peripheral blood macrophages. Smoker AM facilitated mitogen-driven proliferation of homologous PL in a normal fashion, demonstrating the utility of this culture system in distinguishing lymphocyte effects present in autologous cultures.