The capacity of normal murine alveolar macrophages to function as antigen-presenting cells for the initiation of primary antibody-forming cell responses to sheep erythrocytes in vitro.

The precise role of resident alveolar macrophages (AM) in the induction of immune responses to inhaled antigens is not known. In order to gain insight into the immune functions of AM in vivo, the present studies were performed to characterize several immune functional capacities of normal murine AM, to compare these with normal peritoneal macrophages (PM), and to determine the capacity of AM to serve as antigen-presenting cells for the induction of primary antibody-forming cell (AFC) responses to sheep erythrocytes (SRBC) in vitro. We compared the capacities of normal murine AM and of PM to: elaborate interleukin-1 (IL-1), express surface membrane Ia antigen, serve as accessory cells for mitogen-induced blastogenesis, and induce generation of primary AFC responses to SRBC in Mishell-Dutton cultures. We observed that: AM and PM elaborate equivalent IL-1 activity after stimulation with phorbal myristate acetate (PMA); AM "conditioned" with supernatants of concanavilin-A-stimulated spleen cells express surface Ia but do so proportionately less than similarly treated PM; normal AM can serve as accessory cells for mitogen-induced blastogenesis but do so significantly less effectively than do PM; AM substitute poorly for PM with respect to the induction of primary AFC responses to SRBC in standard Mishell-Dutton cultures; however, AM exert potent suppressive activity in these cultures, and this suppression can be reversed by the addition of indomethacin and catalase to cultures, suggesting that both prostaglandins and hydrogen peroxide play suppressive roles; after reversal of suppression in drug-modified Mishell-Dutton cultures, AM can induce primary AFC responses to SRBC but do so less effectively than do similarly treated PM.(ABSTRACT TRUNCATED AT 250 WORDS)