Cytokines related to three major types of cell-mediated immunity in short- and long-term exposures to lead compounds.

Many investigators have posited on the significant influence of lead on the immune system function. However, available data on this topic are not conclusive. Therefore, a study was undertaken to examine associations between lead exposure and levels of cytokines related to the T-helper (TH )-1, TH 2, and TH 17 types of immune response in humans. For these analyses, three population groups were examined: the first consisted of male workers exposed to lead for a short period of time (36-44 days); the second included male workers chronically exposed to lead (13 ± 10 years); and a control group that was composed of male administrative workers with blood lead levels (BLL) < 10 μg/dl. BLL were determined for all study subjects. Thereafter, serum samples were analyzed for the levels of interleukin (IL)-2 (IL-2), IL-4, IL-5, IL-12, IL-13, IL-17A, and interferon (IFN)-γ using a multi-analyte system. The results indicated that the levels of IFNγ IL-2, IL-12 (related to TH 1 cells), IL-4, IL-5, IL-13 (related to TH 2 cells), and IL-17A (related to TH 17 cells) did not change after a short-term exposure to lead (compared to baseline). However, the levels of all of these cytokines were significantly higher in workers chronically exposed to lead than in the controls by 82%, 32%, 81%, 22%, 70%, 42%, and 17% (IFNγ, IL-2, IL-12, IL-4, IL-5, IL-13, IL-17A, respectively). From these studies, we conclude that in humans, a short-term exposure to lead does not affect levels of cytokines related to the TH 1-, TH 2-, and TH 17-mediated immune responses, while chronic exposure modifies their levels. Taken together, these modifications do not evidence an ability of lead to promote specifically one type of immune response in an exposed host.