TUMOR-NECROSIS-FACTOR-ALPHA INDUCTION BY ENDOTOXIN-CONTAINING COAL-MINE DUSTS IN CULTURES OF HUMAN MACROPHAGES AND ITS EFFECTS ON PNEUMOCYTE TYPE-II CELLS

Recent results indicate that tumour necrosis factor alpha (TNF alpha) may have an important role in the pathogenesis of silicosis. Supernata nts of macrophages exposed to quartz and coal mine dust were tested fo r the presence of TNF alpha. Monocytes were isolated from peripheral b lood and cultured for 10-14 days. After in vitro maturation of monocyt es to cells with characteristics of macrophages, they were incubated w ith quartz dust DQ12 and various coal mine dusts from the Ruhr Valley for 24 hr. TNF alpha bioactivity in the supernatants of dust-treated m acrophages was measured in a cytotoxicity bioassay with L929-mouse fib roblasts. Endotoxin, the lipopolysaccharide-containing cell wall compo nent of Gram-negative bacteria, is the most important stimulator of TN F alpha induction in human macrophages. Suspensions of coal mine dusts from the Ruhr Valley and quartz dust DQ12 were therefore analysed for the presence of endotoxin by the very sensitive Limulus amoebocytes l ysate test. Only a few suspensions of coal mine dusts from the Ruhr Va lley contained endotoxin. Only endotoxin-containing dusts stimulated m acrophages to produce TNF alpha. Incubating human pneumocytes type II (line A-549) with TNF alpha as the pure substance led to a transformat ion of these epithelial cells into spindle-shaped cells. This morpholo gical transformation was accompanied by marked inhibition of pneumocyt e type II proliferation.