Effect of all-trans retinol and retinoic acid nutriture on the immune system of chicks.

The effects of all-trans retinol and retinoic acid (RA) on the humoral and cell-mediated immune response and on lymphoid organ weights of broiler chicks were examined. Chicks were fed diets supplemented with retinol or RA at 0, 0.2 and 2.0 micrograms/g diet. The diets were fed continuously from day of hatch or after depletion of hepatic vitamin A reserves. Rapid vitamin A deficiency was induced in chicks by initially feeding the diet containing 2.0 micrograms RA/g diet and subsequently feeding diets containing 0 or 0.2 microgram RA/g diet. Serum antibody hemagglutination titers, in response to intravenous injection of human serum albumin (HSA), were not affected by level or chemical form of vitamin A supplemented in diets. In vitamin A-deficient chicks, there was an inverse relationship observed between the number of peripheral blood lymphocytes obtained per milliliter of blood and their ability to proliferate in response to mitogenic stimulation. Growth of the bursa of Fabricius and the thymus was impaired in chicks fed a vitamin A-free diet. A partial deficiency of vitamin A adversely affected relative bursa weight but not that of thymus. In general, RA was inferior to retinol in maintenance of lymphoid tissue.