Effect of Astaxanthin from Phaffia Rhodozyma on T cell Population and Responsiveness to Mitogen in Splenic Mononuclear Cells of Male Broiler Chicks

Abstract

Effect of feeding astaxanthin (Ax) provided as Phaffia rhodozyma on T cell population and responsiveness to mitogen, concanavalin A (Con A) or phytohemaggulutinin (PHA), of splenic mononuclear cells (MNC) was determined in male broiler chicks. Chicks at1 week of age, were fed ad libitum on diets containing 0, 20 or 100ppm Ax for 7 days. Feeding the diet containing Ax decreased percentage of CD3-positive cells, an indicator of the T cell population in splenic lymphocytes. Feeding the diet containing 20ppm Ax decreased percentage of CD4-positive cells estimated as the indicator of helper T cells, but no modulation was observed by feeding the diet containing100ppm Ax. Percentage of CD8-positive cells, an indicator of cytotoxic T cell, was not affected by feeding diets containing either 20 or 100ppm Ax. T cell proliferation stimulated with Con A was enhanced by feeding diet containing 20ppm Ax, but not affected by 100ppm Ax. Feeding diets containing 20 and 100ppm Ax enhanced the proliferation of splenocytes against PHA. Feeding diets containing Ax showed no effect on interleukin(IL)-2mRNA expression in splenocytes stimulated by Con A estimated as the T cell proliferation promoting factor. IL-2 like activity was slightly, but significantly, decreased by feeding diet containing 20ppm Ax. IFN-γmRNA expression, estimated as a T cell activator under condition of Con A stimulation, was higher in chicks fed the diet containing 20ppm Ax. These results suggest that proliferation and cytokine expressions of splenic T cells in response to feeding Phaffia rhodozyma containing Ax were independent of the dietary Ax concentration or total Ax intake. The enhancement of T cell proliferation by feeding 20ppm Ax might be caused by changes in IFN-γ rather than IL-2 production in the chick splenocytes.