Cytokine production by rabbit alveolar macrophages: differences between activated and suppressor cell phenotypes

The differences between cytokine-producing profiles of activated macrophages (A-M phi) and suppressor macrophages (S-M phi) were examined. A-M phi, which exhibited cytotoxicity against RK-13 cells, were generated from resident rabbit alveolar M phi by treatment with lymphokine solution (culture fluids of rabbit spleen cells stimulated with concanavalin A [Con A]). S-M phi, which were able to inhibit cellular proliferations of rabbit spleen cells stimulated with Con A, were generated from resident alveolar M phi by treatment with 1-methyladenosine (an immunosuppressive molecule in tumourous ascites fluids). When A-M phi were stimulated with lipopolysaccharide (LPS) in vitro, the cells produced significantly more interleukin (IL)-1 (approximately 1.4 times), IL-6 (approximately 2.1 times), IL-12 (approximately 60 times), and tumour necrosis factor-alpha (TNF-alpha) (approximately 37 times) than did resting macrophages (R-M phi) stimulated with LPS as control cells. After the stimulation with LPS, both A-M phi and R-M phi did not produce transforming growth factor-beta (TGF-beta). In contrast, when S-M phi were stimulated with LPS in vitro, the cells produced significantly more TGF-beta (approximately 1.6 times) and significantly less IL-6 (approximately 1.8 times) than did control cells. Also, S-M phi did not produce IL-1, IL-12, and TNF-alpha into their culture fluids after the stimulation with LPS. These results show the differences between cytokine-producing profiles of A-M phi and S-M phi, and characteristics of their cytokine-producing profiles are analogous to T cell subsets. Differences displayed in the cytokine profiles may contribute to the effector (A-M phi) or the suppressor (S-M phi) functions of alveolar M phi.