Normal and sarcoid alveolar macrophages differ in their ability to present antigen and to cluster with autologous lymphocytes.

Human bronchoalveolar macrophages from normal individuals function poorly as accessory cells for the presentation of common recall antigens. In sarcoidosis, alveolar macrophages (AM) are reported to be effective accessory cells for the presentation of such antigens. In this study normal and sarcoid AM were compared with blood monocytes for their ability to act as accessory cells in presenting tuberculin purified protein derivative (PPD) and streptokinase-streptodornase (SKSD) to autologous T lymphocytes, or to form spontaneous, antigen- or mitogen-induced clusters with the T cells. When compared to autologous monocytes, normal AM failed to present the two recall antigens effectively. Likewise normal AM formed very few clusters with T lymphocytes when compared to monocytes, even in the presence of antigens or the mitogen phytohaemagglutinin (PHA). In contrast, sarcoid AM presented both antigens as effectively, and were equally effective as monocytes in forming clusters with T lymphocytes, spontaneously and in further response to antigen or mitogen. The results suggest that in sarcoidosis enhanced accessory cell function and enhanced cluster formation may be related features of bronchoalveolar macrophage populations.