Production of Tumor Necrosis Factor‐α by Alveolar Macrophages of Lung Cancer Patients

The abilities of human alveolar macrophages (AM) obtained from healthy donors and patients with lung cancer to produce tumor necrosis factor (TNF) were compared with those of their blood monocytes after activation with lipopolysaccharide (LPS). TNF activity was assayed by measuring cytotoxicity against actinomycin D‐treated L929 cells and TNF was determined quantitatively by sandwich enzyme‐linked immnnosorbent assay (ELISA) with polyclonal and monoclonal antibodies against TNF‐α. Unstimulated AM from healthy donors released variable amounts of TNF spontaneously, whereas blood monocytes did not. When treated with LPS for 24 h, AM and monocytes produced TNF dose‐dependently, but TNF production by AM was significantly more than that by blood monocytes. This TNF activity was inhibited completely by monoclonal anti‐TNF‐α antibody. Macrophages generated by in vitro maturation of monocytes induced by granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) produced more TNF than freshly isolated monocytes. No difference was found in the abilities of AM from healthy donors and patients with lung cancer to produce TNF after activation stimuli. These observations suggest that human AM may be important in in vivo antitumor defense of the lung through TNF‐α production.