Does aluminium stimulate the immune system in male rats after oral exposure?

The influence of oral aluminium exposure on the immune system was studied in rats. Male rats were exposed to soluble and labile Al in acidic drinking water (0-500 mg Al/l) for 7-9 weeks. The concentration of Al in femur bone was higher in rats exposed to 50 and 500 mg Al/l (mean concentration 277 and 599 ng Al/g) than in control rats (150 ng Al/g). The Al concentration in blood plasma could only be quantified in the 500 mg/l group (mean 2.7 ng/ml), whereas the concentrations in the control and 50 mg/l groups were low (< 2 ng Al/ml). Exposure of 4-13-weeks-old rats to the highest Al concentration caused an increased number of splenocytes, whereas exposure of 9-16-weeks-old rats to 500 mg Al/l caused an increased number of thymocytes. Moreover, the proliferative response of splenocytes to the mitogen Con A (2 micrograms/ml) was increased by exposure of the 9-16-weeks-old rats to 500 mg Al/l as compared with the controls. The results indicate that oral Al exposure caused a slight stimulation of some immune functions in the rat at Al plasma concentrations normally found in the human population (< 10 ng Al/ml).