ELEVATION OF RAINBOW-TROUT ONCORHYNCHUS-MYKISS MACROPHAGE RESPIRATORYBURST ACTIVITY WITH MACROPHAGE-DERIVED SUPERNATANTS

A variety of supernatants were prepared by stimulating rainbow trout O ncorhynchus mykiss head kidney macrophages with lipopolysaccharide (LP S), tumor necrosis factor alpha (TNF-alpha), or a leucocyte-derived ma crophage-activating factor (1-MAF), individually and in combination, I f generated using a 12-h stimulation period, such supernatants were fo und to elevate significantly the respiratory burst activity of target macrophages; that is, they contained a macrophage-derived MAF (m-MAF), but supernatants generated using a shorter incubation period showed n o significant activity, Combinations of these treatments were particul arly effective in generating m-MAF-containing supernatants, The elevat ion of respiratory burst activity by supernatants generated using comb ined treatments could be partially inhibited by prior treatment of the target macrophages with anti-TNF-alpha receptor 1(TNFR1) monoclonal a ntibodies (mAbs), Similarly, treatment of macrophages with combination s of 1-MAF and m-MAF generated supernatants with potent m-MAF activity and this activity was partially inhibited by prior treatment of the t arget cells with anti-TNFR1 mAb, In addition, the presence of anti-tra nsforming growth factor beta 1 (TGF-beta 1) serum while generating the se latter supernatants resulted in significantly increased m-MAF activ ity, Such data suggest that fish leukocytes secrete a variety of poten t macrophage-activating (TNF-alpha) and deactivating (TGF-beta) factor s.