with BLL (average 39 μg/dL), serum IgG was negatively associated with cumulative lead exposure, and naïve memory T cells (CD3+/CD45RA+) were positively associated with cumulative lead exposure. In a study of Portuguese workers that evaluated immune cell profiles, Garcia-Leston et al. (2011) demonstrated a significant decrease in percentages of CD8+ cells with a concurrent increase in the CD4+: CD8+ ratio in exposed people who had BLLs of 40 μg/dL or higher. In a clinical context, this finding could be significant (although the extent of CD8+ suppression needed for a clinical outcome is unknown) inasmuch as a decrease in CD8+ cells could increase susceptibility to viral infections or decrease antitumor immune mechanisms.
Studies of Turkish storage-battery workers who had a median BLL of 75 μg/dL indicated that it was associated with statistically significant decreases in TH cells, serum IgG, IgM, and some serum complement components (Basaran and Undeger 2000). In vitro functional aberrations, including changes in neutrophil chemotaxis and random movement, were also noted in the workers. The latter findings were in keeping with the study by Queiroz et al. (1993) that demonstrated defective neutrophil function (chemotaxis and production of ROS) in workers who had a lower average BLL of 41 μg/dL (range 14.8-91.4 μg/dL). Impaired neutrophil movement was thought to be due to lead-induced changes in cell membrane fluidity.
Although most worker studies have examined the immunotoxic effects of lead exposure on men, a study by Qiao et al. (2001) examined women who worked an average of 12 years in printing houses in China. The mean air lead concentration was about 25 (± 19) μg/m3, and average BLLs of the workers were about 29 (± 15) μg/dL; the study referent group had an average BLL of 12.4 μg/dL. Assessments of circulating lymphocyte subset concentrations in both referent and lead-exposed women indicated that “memory” TH cell levels were increased in the exposed workers, whereas NK-cell and B-cell concentrations were statistically significantly reduced. The reduction in blood NK cells in lead-exposed women agrees with the results of Sata et al. (1997), who examined circulating NK cells in male workers who had an average BLL of 18 μg/dL (range 7-35 μg/dL). Also in that study, BLL correlated significantly with serum IgA and IgE concentrations; IgE levels were greatest in workers who had BLLs over 60 μg/dL. In a study that examined battery workers in Korea (Heo et al. 2004), serum IgE concentration correlated significantly with BLL; values were statistically significantly higher in workers who had BLLs of 30 μg/dL or higher than in those who had BLLs under 30 μg/dL. In a study of lead-exposed workers who had BLLs of 9-46 μg/dL, Valentino et al. (2007) examined changes in cytokine concentrations. The results demonstrated that workers had statistically significantly higher concentrations of the anti-inflammatory cytokine inter-leukin-10 (IL-10) and a tendency toward higher concentrations of the proinflammatory cytokine tumor necrosis factor-α (TNF-α) in occupationally exposed male workers than in sex-matched and age-matched controls.