Immune-related genes of the Japanese flounder, Paralichthys olivaceus

Abstract

Fish have many nonspecific and specific immune mechanisms, with humoral and cellular mechanisms to resist infectious diseases. However, the biodefense and immune-related systems of fish are poorly understood at the molecular level. We have isolated many putative biodefense and immuno response-related genes from the Japanese flounder, Paralichthys olivaceus; these include cytokines (interleukin-1β, tumor necrosis factor, chemokines, etc), cytokine receptors (TNFR-1 and −2, IL1R, IL6R, chemokine receptors, etc.), cell surface molecules (T-cell receptors, IgM, IgD, CD3, CD8, toll-like receptors, etc.), transcription factors (IRFs, CEBP, Stat3, etc.), antimicrobial proteins (lysozymes, transferrin, Mx), proteases, and protease inhibitors. We have determined the complete sequences of several biodefense and immuno response-related genes that were originally isolated as partial fragments from expressed sequence tag (EST) analysis. We have also found several virus-, bacterial endotoxin-, and mitogen-induced genes in Japanese flounder leukocytes. Some of these genes have no similarity to previously reported genes or peptides in DNA/protein databases. The existence of unidentified genes that are upregulated by viruses, bacterial endotoxins, or mitogens in fish suggested that fish have specific immune and defense mechanisms.