Interleukin 1-like thymocyte and fibroblast activating factors from rat alveolar macrophages exposed to silica and asbestos particles.

Abstract

The present study was designed to evaluate the immunostimulatory and fibrogenic factor(s) from alveolar macrophages (AM) after the in vitro exposure to silica or asbestos particles. Interleukin 1(IL-1)-like thymocyte proliferation activity was detected in the supernatants from rat AM cultures stimulated in vitro with silica or asbestos particles in a dose-dependent manner. In addition to this thymocyte proliferation activity, those supernatants from silica-or asbestos-stimulated AM cultures also exhibited fibroblast proliferation activity. Both of these activities were enhanced by addition of lipopolysaccharides (LPS) to silica- or asbestos-stimulated AM cultures. It was shown that both of the activities in AM culture supernatants were produced by AM during the 24 hr-incubation, and that these AM products were non-dialyzable, rather heat-stable, and trypsin-sensitive in nature. The gel filtration of AM culture supernatants revealed that the major peaks of both activities ranged in the low molecular weight (18000-25000 daltons), and also in the high molecular weight (75000-100000 daltons) fractions, which appeared to be the aggregates of the low molecular weight components. These results indicate at least that fibroblast proliferation activity in AM culture supernatants is partly attributable to IL 1-like factor. This provides an important implication regarding the pathogenic role of IL 1 from AM in pulmonary disorders after exposures to mineral dusts.