This study demonstrated the mechanisms of boron effects in a rat model and provided a scientific basis for the rational of boron use. These findings were achieved by investigating the effects of boron (10, 20, 40, 80, 160, 320, and 640 mg/L in drinking water or 1.5, 3, 6, 12, 24, 48, and 96 mg/kg BW) on rat serum immunoglobulins (IgGs), splenic cytokines, lymphocyte subsets, as well as on lymphocyte proliferation and apoptosis. Addition of 20 (3) and 40 (6) mg/L (mg/kg BW) of boron to drinking water significantly increased rat serum IgG concentrations, splenic IFN-γ and IL-4 expression as well as the number of splenic CD3+, CD4+ and proliferating cell nuclear antigen (PCNA)+ cells. Supplementation of drinking water with 40 mg/L (6 mg/kg BW) boron also markedly increased splenic IL-2 expression and the CD4+/CD8+ cell ratio and reduced splenic CD8+ cell number. Supplementation with 80 mg/L (12 mg/kg BW) boron significantly increased CD3+ and PCNA+ cell numbers (P < 0.05) and decreased the IL-10 expression in the spleen. Addition of 320 (48) and 640 (96) mg/L (mg/kg BW) boron markedly reduced the serum IgG concentrations; splenic IL-2 and IL-10 expression; the number of CD3+, CD4+ and PCNA+ cells; and increased the number of splenic CD8+ and caspase-3+ cells and promoted caspase-3 expression in CD3+ cells. In conclusion, these findings suggest that the supplementation of rat drinking water with 20(3) and 40(6) mg/L (mg/kg BW) boron can markedly enhance humoral and cellular immune functions, while boron concentrations above 320 mg/L (48 mg/kg BW) can have an inhibitory effect or even toxicity on immune functions. These results exhibit a U-shaped response characteristic of low and high doses of boron supplementation on immune function and imply that proper boron supplementation in food for humans and animals could be used as an immunity regulator.
Keywords: Boron; Immune function; Lymphocyte; Proliferation and apoptosis; Spleen.