Tumor necrosis factor alpha (TNFα)-like factor produced by macrophages in rainbow trout, Oncorhynchus mykiss

The presence of a Tumor Necrosis Factor alpha (TNFα)-like molecule has been suggested in fish by biological assays and biological and antigenic cross-reactivities with human TNFα. In the present study, whether rainbow trout macrophages produce TNFα was examined. Murine recombinant TNFα (m-rTNFα) was used as the standard mammalian TNFα. The supernatants were harvested from trout macrophage culture stimulated with lipopolysaccharide (LPS) and then passed through a Polymyxin B column to remove LPS. Results show that trout macrophage culture supernatants exhibit TNF-like activities. The supernatants significantly enhanced neutrophil migration and macrophage respiratory burst activity as assessed by NBT reduction test. The supernatants were also highly cytotoxic to murine L929 cells, which are known to be sensitive to mammalian TNFα. The biological activities of TNF in the trout macrophage culture supernatant was determined as 2·6 U ml−1in the presence of actinomycin D. This indicates biological cross-reactivity of trout TNFα-like factor on mammalian cells. Moreover, these activities were inhibited by a rabbit anti-mTNFα antibody. These results suggest that rainbow trout macrophages produce a TNFα-like factor that is similar to the mammalian TNFα in functions.