Effects of oxidative stress on immunosuppression induced by selenium deficiency in chickens.

Selenium (Se) is an important nutritional trace element possessing immune-stimulatory properties. The aim of this 75-day study was to investigate effect of oxidative stress on immunosuppression induced by selenium deficiency by determining antioxidative function, morphological changes, DNA damage, and immune function in immune organ of chickens. One hundred sixty 1-day-old chickens (egg-type birds) were randomly assigned to two groups of 80 each and were fed on a low-Se diet (0.032 mg/kg Se) or a control diet (0.282 mg/kg Se, sodium selenite), respectively. Se contents in blood and immune organ (thymus, spleen, bursa of Fabricius) were determined on days 30, 45, 60, and 75, respectively. Antioxidative function was examined by total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and xanthine oxidase (XOD), and oxidative damage was examined by malondialdehyde (MDA) detection. DNA damage was measured by comet assay, and immune function was examined by determining serum interleukin-1β (IL-1β), interleukin-2 (IL-2), and tumor necrosis factor (TNF) contents. The results showed that Se concentrations in the low-Se group were significantly lower (P < 0.05) than in the control group. Low-Se diet caused a decrease in the activities of T-AOC, SOD, GSH-Px, and an increase in XOD activity and MDA content. Pathological lesions and DNA damage of immune tissues were observed in low-Se group, while the serum IL-1β and IL-2 contents decreased, and TNF content increased. The present study demonstrated that chickens fed deficient in Se diets exhibited lesions in immune organs, decreased serum IL-1β, IL-2 content, and serum TNF content, indicating that oxidative stress inhibited the development of immune organs and finally impaired the immune function of chickens.