Effect of fluoride exposure on different immune parameters in humans

T regulatory (Treg) cells play an important role in the modulation of the immune response, and are implicated in the pathogenesis of autoimmune diseases. Many people is exposed to fluoride (F), mainly through drinking water.

The aim of this work was to assess the possible effect of F exposure on different immune parameters, mainly Treg cells.

We studied 61 subjects from a community of the state of Durango, Mexico, where the population is exposed to F levels over 2.0 ppm in drinking water. Peripheral blood mononuclear cells (PBMC) were isolated and the level and function of Treg cells was analyzed by flow cytometry and cell proliferation assays. In addition, we detected the presence of apoptotic cells, the expression of TLR/CD14, and the in vitro synthesis of TNF-α by monocytes.

We found a negative correlation between urinary F and percentage of CD4(+)CD25(+) Treg cells (r = -0.55, P < 0.001). Accordingly, a defective function of these cells was detected in 30% of individuals exposed to F. In contrast, a positive association between levels of CD4(+)TGF-β(+) or CD4(+)IL-10(+) Treg lymphocytes and F urine concentrations was detected. In addition, a negative correlation was detected between the F urinary levels and the proportion of apoptotic cells, in PBMC or T cells or monocytes (P < 0.05 in all cases). Finally, no apparent association between F exposure and TLR4/CD14 expression or the synthesis of TNF-α was detected.

Our data suggest that F exposure exerts a complex and relevant effect on Treg cells in humans.