Altered human monocyte/macrophage function after exposure to diesel exhaust particles

The relationship between immune defense mechanisms and environmental pollutants has been a focus of intensive research during the last decade. In animal experiments, diesel exhaust particles (DEP) have been shown to exert adjuvant effects on the IgE response against aeroantigens and to compromise broncho-pulmonary immune defense. Important target cells are monocytes/alveolar macrophages which display the important functions of phagocytosis, antigen-presentation and modulation of inflammatory processes. To further evaluate the influence of DEP upon these cells, we investigated whether exposure to suspended DEP would change the phagocytic capacity and the tumor necrosis factor alpha (TNF-alpha) release of human peripheral monocytes/alveolar macrophages. Our results demonstrated a dose-dependent reduction of phagocytosis (p < 0.001) and an additional increase of an ongoing TNF-alpha response (p < 0.005). These findings may help to link exposure to environmental pollutants to such biologic effects as increased susceptibility to broncho-pulmonary disease or facilitated sensitization against aeroallergens.