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

The presence of a Tumor Necrosis Factor alpha (TNF alpha)-like molecule has been suggested in fish by biological assays and biological and antigenic c rossreactivities with human TNF alpha. In the present study, whether rainbo w trout macrophages produce TNF alpha was examined. Murine recombinant TNF alpha (m-rTNF alpha) was used as the standard mammalian TNF alpha. The supe rnatants were harvested from trout macrophage culture stimulated with lipop olysaccharide (LPS) and then passed through a Polymyxin B column to remove LPS. Results show that trout macrophage culture supernatants exhibit TNF-li ke activities. The supernatants significantly enhanced neutrophil migration and macrophage respiratory burst activity as assessed by NET reduction tes t. The supernatants were also highly cytotoxic to murine L929 cells, which are known to be sensitive to mammalian TNF alpha. The biological activities of TNF in the trout macrophage culture supernatant was determined as 2.6U ml(-1) in the presence of actinomycin D. This indicates biological cross-re activity of trout TNF alpha -like factor on mammalian cells. Moreover, thes e activities were inhibited by a rabbit anti-mTNF alpha antibody. These res ults suggest that rainbow trout macrophages produce a TNF alpha -like facto r that is similar to the mammalian TNFa in functions. (C) 2001 Academic Pre ss.