Effects of dietary polyunsaturated fatty acids on in vivo splenic cytokinemRNA expression in layer chicks immunized with Salmonella typhimurium lipopolysaccharide

Effects of dietary polyunsaturated fatty acids (PUFA) on immune responses i n poultry have been reported. However, effects on the underlying mechanisms , such as the role of cytokines, have not been documented because the neces sary tools were lacking. Recently, primer sets for chicken interleukin (IL) -1 beta, IL-2, interferon-gamma (IFN-gamma), myelomonocytic growth factor ( MGF), and transforming growth factor (TGF)-beta (2) have become available. Therefore, in the present study we first examined the in vivo effects of an inflammatory challenge with Salmonella typhimurium lipopolysaccharide (LPS ) on cytokine profiles in growing laying-type chicks. Second, we examined w hether dietary fat sources affected the observed cytokine profiles. Two hun dred forty chicks were assigned in a 2 x 4 factorial design of treatments, with injection with LPS or saline and dietary fat source as factors. Factor s were i.v. injection with S. typhimurium LPS or saline (control) and four dietary fat sources: corn oil, linseed oil, menhaden oil, and tallow. Two h ours after injection, birds were killed, and their spleens were removed for RNA extraction. Reverse transcription polymerase chain reactions with prim er sets for chicken IL-1 beta, IL-2, IFN-gamma, MGF, TGF-beta (2), and beta -actin were performed with RNA samples pooled by pen. The expression of cy tokine mRNA was expressed relative to the level of beta -actin mRNA. Interl eukin-1 (P < 0.001), MGF (P < 0.0001), IL-2 (P < 0.001), and IFN-gamma (P < 0.001) mRNA expressions were enhanced by challenge with LPS. Immunization treatment had no effect on TGF-beta2 or beta -actin expression. Dietary tre atment did not affect mRNA expression of IL-1, MGF, IFN-gamma, TGF-beta (2) , or beta -actin. Interleukin-2 expression in LPS-injected birds that were fed the fish-oil-enriched diet was enhanced (P = 0.05). The present study i ndicates that in vivo effects of immune challenge on cytokine mRNA expressi on can be measured in poultry. The observation that mRNA level of IL-2, but not the mRNA levels of IFN-gamma or MGF, is enhanced by dietary fish oil a t 2 h suggests that dietary PUFA at this moment initially affected naive T lymphocytes.