Expression of immune genes in turbot (Scophthalmus maximus) fed a nucleotide-supplemented diet.

Turbot (Scophthalmus maximus) fed a control or nucleotide-supplemented diet for 15 weeks were examined for the relative expression of a number of immune genes. Genes analysed included those involved in specific immune responses, such as immunoglobulin M (IgM) and recombinase activating gene I (RAG-1), and a number of genes important for nonspecific defences (transferrin, lysozyme, cytokines). After normalising the data to the expression of a housekeeping gene (beta-actin) in each sample analysed, it was found that IgM and RAG-I gene expression were both significantly increased in the gill and spleen of fish fed the nucleotide-supplemented diet but decreased in the kidney of these fish. Transferrin expression was unaffected by the nucleotide supplementation, as was the expression of the cytokine gene transforming growth factor beta. Lysozyme expression was significantly decreased in the spleen and kidney of fish fed the nucleotide-supplemented diet, with no effect apparent in the gill. In contrast, a second cytokine gene examined, interleukin-1beta, showed a significant increase in expression in the kidney of the nucleotide-supplemented group. These data are discussed in relation to the differential effects seen, the function of the molecules examined and the potential for dietary modulation of fish health. (C) 2003 Elsevier Science B.V. All rights reserved.