Antiproliferative properties of human alveolar macrophages

Objective: The aim of our study was to determine whether macrophages from lung cancer patients could acquire antitumoral properties in an in vitro model. Methods: We isolated macrophages from bronchoalveolar lavages performed in two groups of patients: patients with lung cancer and patients with lung infection. All patients were smokers. We used the inhibition of incorporation of H-3-thymidine by U937 tumoral cells as an in vitro cytostatic assay. Results: When stimulated by gamma interferon, alveolar macrophages either from lung cancer patients or from patients with lung infection induced cytostasis of proliferating U937 tumoral cells. This effect could be reproduced by using the supernatants of cultures of activated macrophages. When using optimal doses, gamma interferon showed an increased activity as compared with lipopolysaccharide. The combination of these two compounds was no more effective than gamma interferon alone in cancer patients. A macrophage/U937 tumoral cell ratio of 1/1 was sufficient to achieve a near-maximal cytostatic effect. Conclusions: Our results demonstrate that it is possible to activate, in vitro, alveolar macrophages from lung cancer patients by stimulation with gamma interferon. These macrophages acquire antiproliferative properties against a sensitive tumoral cell line.