Monocyte-macrophage system and polymorphonuclear leukocytes in workers exposed to low levels of metallic mercury

Our previous research ŽSoleo L, Vacca A, Vimercati L et al. Occup Environ Med 1997;54:437 442. showed a reduction in tumor necrosis factor- ŽTNF- . serum levels in workers with prolonged exposure to low doses of inorganic mercury, suggesting an in vivo functional defect of the monocyte-macrophage system. On this basis, here we wondered whether workers exposed to lower doses of metallic mercury displayed possible changes in the monocyte-macrophage system. In this particular cohort of workers, we also sought for the effects of the exposure on the polymorphonuclear leukocytes ŽPMNL. chemotaxis. The monocyte-macrophage system and the natural killer ŽNK. cells were examined in 19 exposed workers and in 25 unexposed workers, as the control group Žcontrols.. Specifically, the circulating monocyte-macrophage cells and their CD13, CD15 and CD33 subsets, serum cytokines ŽIL-8, GM-CSF and TNF- . and the NK cells were analyzed. In seven exposed and seven controls randomly chosen workers the PMNL chemotaxis was also assessed. The selected indicator of mercury exposure were the levels of mercury in the urine ŽU-Hg., that was significantly higher in exposed workers than the controls Ž9.7 5.5 g l and 2.4 1.2 g l, respectively.. None of the exposed workers had shown signs of either acute or chronic inorganic mercury toxicity or any form of hypersensitivity. Several immunological variables tested, monocyte-macrophage cells and their subsets, NK cells and serum cytokines overlapped between the exposed and the control workers. When the workers were considered as a whole Žexposed plus controls., no correlation was found between current U-Hg and all immunological parameters. However, when exposed workers were studied separately, an inverse correlation was disclosed between cumulative U-Hg and cells Žas percentage. expressing the CD13 Žr 0.599; P 0.007. and CD15 Žr 0.614; P 0.005. molecules, and NK cells Žr 0.455; P 0.05.. Moreover, a significant impairment in