Effect of 28-day oral administration of silver nanocolloid on the peripheral blood leukocytes in mice

Silver nanoparticles, which have found a wide range of applications owing to their antimicrobial properties, are also recommended as dietary supplements in alternative medicine. Studies on rodents confirm that nanosilver is absorbed from the digestive tract into the bloodstream, which implies its possible interactions with leukocytes. The objective of the experiment discussed herein has been to determine the effect of 28-day oral administration of different doses (0.25, 2.5, 25 ppm) of commercial silver nanocolloid on hematological parameters, percentages of particular lymphocyte populations and activity of the peripheral blood leukocytes in mice. All the tested colloid doses decreased the counts of monocytes in the animals’ blood and induced phenotypic modifications among lymphocytes: an increase in CD4+/CD8+ T cell distribution, a decrease in NK and NKT cell distribution (doses of 0.25 and 2.5 ppm) and an increased CD4+:CD8+ ratio (25 ppm). Silver nanocolloid also affected the activity of cells, depressing the proliferation of lymphocytes (0.25 ppm) and stimulating phagocytosis as well as the respiratory burst of granulocytes and monocytes (all doses). The results verify the influence of orally administered silver colloid on the peripheral blood leukocytes, at the same time implying the potential risk of developing an inappropriate immune response of an organism exposed to prolonged administration of this substance.