Tumor necrosis factor-alpha in low doses activated rat peritoneal macrophages and intensified production of reactive oxygen species (zymosan-depended chemiluminescence). Single or 2-fold incubation with tumor necrosis factor-a activated and preactivated human blood macrophages and promoted oxidative modification of low-density lipoproteins (increased their mobility in agarose gel). Antioxidants (potassium phenosan, probucol, and desferal) suppressed oxidative modification of low-density lipoproteins induced by nonactivated, preactivated, and activated macrophages. Our results show that antioxidants hold much promise for the prevention and therapy of atherosclerosis.