RATIONALE: Over the past 50 years individuals in westernized societies have been increasingly exposed to mercury (e.g. through contaminated fish and dental amalgam) and fluoride (e.g. through drinking water, toothpaste and gels). Given the increasing incidence of allergic diseases and the known immunomodulatory effects of these agents, we investigated their potential allergy-promoting activity.
METHODS: Peripheral blood mononuclear cells (PBMC) from 4 individuals were cultured up to seven days in culture medium or in culture media containing Con A in the presence or absence of mercuric chloride (HgCl) or sodium fluoride (NaF). Supernatants were harvested on days 2, 4 and 6 and IL-4 and gamma-IFN concentrations were measured by ELISA.
RESULTS: HgCl and NaF significantly suppressed Con A-induced gamma-IFN production. Maximum suppression of gamma-IFN production by HgCl occurred on day 6 (10.4% +/- 9.4% of the Con A response) and by NaF on day 4 (8.3% +/- 7.2%). In contrast, HgCl and NaF significantly increased Con A -induced IL-4 production, with a maximum on day 4 (362.9% +/- 365%) and day 2 (660.8% +/- 894.72%), respectively. Neither NaF nor HgCl significantly altered cytokine production in unstimulated lymphocytes.
CONCLUSIONS: HgCl and NaF seem to selectively suppress Th1 activity and stimulate Th2 cytokine production in vitro. Although preliminary, these findings suggest that human exposure to mercury or fluoride may be playing a role in the observed increased incidence of allergic diseases in the industrialized world.