Molecular cloning of rock bream (Oplegnathus fasciatus) tumor necrosis factor-α and its effect on the respiratory burst activity of phagocytes

Rock bream (Oplegnathus fasciatus) tumor necrosis factor-α (rbTNF-α) gene was cloned, recombinantly produced, and the effect of the recombinant rbTNF-α on the respiratory burst activity of rock bream phagocytes was analyzed. Structurally, genomic DNA of rbTNF-α was comprised with four exons and three introns, and deduced amino acid sequence of its cDNA possessed the TNF family signature, a transmembrane domain, a protease cleavage site, and two cysteine residues, which are the typical characteristics of TNF-α gene in mammals and fish. The chemiluminescent (CL) response of rock bream phagocytes was significantly enhanced by pre-incubation with recombinant rbTNF-α, when opsonized zymosan was used as a stimulant of the respiratory burst. However, CL enhancing effect of the recombinant rbTNF-α was very weak when the respiratory burst activity of phagocytes was triggered with phorbol-12-myristate-13-acetate (PMA) instead of zymosan. These results suggest that rock bream TNF-α might have an ability to prime the respiratory burst activity of phagocytes against receptor-mediated phagocytosis inducing stimulants, such as zymosan, but have little ability against stimulants not accompanying receptor-mediated phagocytosis.