Human alveolar macrophage regulation of lymphocyte proliferation.

Human alveolar macrophages obtained by bronchoalveolar lavage have different accessory cell characteristics than do autologous, peripheral-blood-derived macrophages for the support of lymphocyte proliferative responses. To further investigate these differences, we performed mixing experiments in which variable numbers of the 2 macrophages were cocultured and assayed for support of mitogen-(phytohemagglutinin; PHA) and antigen- (streptokinase-streptodornase; SK-SD) stimulated proliferation of purified autologous lymphocytes. Alveolar macrophages promoted greater lymphocyte proliferation, in proportion to their added number in coculture with peripheral-blood-derived macrophages, when using a suboptimal concentration of PHA. In contrast, even small numbers of alveolar macrophages suppressed lymphocyte proliferation supported by peripheral-blood-derived macrophages when using the optimal concentration of PHA or the antigen SK-SD. The data indicated that diminished support exhibited by alveolar macrophages for...