Dietary supplementation with vitamin E modulates avian intestinal immunity.

The effect of dietary vitamin E on immunoglobulin A (IgA) antibody production, which acts as the first line of defence at the intestinal mucosa, has not been evaluated in chickens. In the present study the impact of the inclusion of supplementary levels of vitamin E to the diet, on total and antigen-specific IgA antibody titres, T-cell subsets and Ia+ cells, was assessed. From hatching, chickens received a maize-based diet which was supplemented with either 25, 250, 2500 or 5000 mg dl-alpha-tocopherol acetate/kg. Primary immunisation with tetanus toxoid (T. toxoid) emulsified in a vegetable oil-in-water adjuvant was administered by the intraperitoneal route at 21 d of age. At 35 d of age all birds received an oral booster vaccination of T. toxoid. Significantly higher total IgA antibody titres were present in the day 42 intestinal scrapings of birds receiving the 5000 mg/kg vitamin E-supplemented diet (VESD) (P=0.05) and a notable increase was observed in birds receiving the 250 mg/kg VESD (P=0.06). At days 21 and 42 total serum IgA antibody titres of birds receiving the 250 mg/kg VESD was significantly higher (P<0.05) than the control birds. Following immunisation with T. toxoid, birds receiving the 250 and the 5000 mg/kg VESD had elevated anti-T. toxoid IgA antibody titres in final day intestinal scrapings, which, for the latter group was statistically significant (P=0.02). Both of these groups also demonstrated increased titres of anti-T. toxoid IgA in the serum at day 42. Birds receiving the 250 mg/kg VESD exhibited a notable increase in the percentage of T-helper cells and Ia+ cells in peripheral blood on day 26. The results illustrate the potential for some levels of dietary vitamin E supplementation to act as an immunomodulator of total and antigen-specific IgA antibody.