| The genetic selection for commercial traits in poultry could have an impact on the immune competence. We have demonstrated that broiler chicks compared to layers may have suppressed inflammatory responses demonstrated by lower in vivo and in vitro responsiveness to LPS. The suppressed inflammatory responses in broilers correlate with decreased pro-inflammatory cytokine MGF (P < 0.001), IL-1beta (P = 0.093), and IFNgamma (P = 0.055) mRNA expression, and increased TGFbeta2 mRNA expression (P = 0.059) in spleen cell cultures. The suppressed inflammatory responses may be compensated by enhanced T cell activity. Further, we investigated the effect of several dietary levels of vitamin E (0, 10, 17.5, 25, 37.5, 50, 100, 200 IU/kg of diet) on the immune responses of broilers. We demonstrated that high dietary vitamin E levels are not consistently immunoenhancing. While high dietary vitamin E levels enhance the antibody response to attenuated IBV, they are less effective than medium levels in generation of antibody response to SRBC, modulation immune responses to polyclonal mitogens, and modulating heterophilia. Effects of low (0 IU/kg), medium (30 IU/kg) and high (200 IU/kg) vitamin E levels on the peripheral lymphocyte concentrations, CD4+/CD8+ lymphocyte ratios, and mRNA expression of chicken IL-1beta, MGF, IL-2, IFNgamma, and TGFbeta in vivo after LPS administration were analyzed.; Dietary vitamin E decreased MGF mRNA (P = 0.049) in a dose-dependent manner, but had no effect on expression of other cytokines. The decreased expression of the proinflammatory cytokine MGF could explain the immunomodulatory effect of vitamin E in inflammation and suggest that higher dietary vitamin E levels are more potent than moderate vitamin E levels in modulation of inflammatory responses. However, the decrease in CD4+/CD8+ ratio at moderate vitamin E level suggests that moderate and high dietary vitamin E levels have different effects on T cell function. |
