We report on the regulation of pro-inflammatory functions of goldfish macrophages and induction of gene expression by recombinant goldfish CSF-1 (rgCSF-1). Recombinant goldfish TNFalpha-2 (rg TNFalpha-2), rgIFNgamma but not rgTGFbeta induced time-dependent increase of CSF-1 expression in macrophages. Treatment of goldfish macrophages with rgCSF-1 increased expression of several immune genes including CXCL-8 (=IL-8), CCL-1, TNFalpha-1, TNFalpha-2, IL-1beta-1, IL-1beta-2, IL-12-p35, IL-12-p40, IFN, IL-10 and iNOS A and B. The rgCSF-1 treatment did not significantly alter the mRNA levels of TGFbeta and NRAMP in macrophages up to 48h post treatment. However, at 72h post treatment, the expression of TGFbeta increased whereas that of NRAMP decreased. The treatment of macrophages with rgCSF-1 enhanced their respiratory burst and nitric oxide responses that were abrogated after addition of soluble CSF-1 receptor (sCSF-1R) to cell cultures. Macrophages exhibited a concentration-dependent chemotactic response toward rgCSF-1 as well as an increase in phagocytic activity that was abrogated after addition of sCSF-1R to cell cultures. Our results indicate that in addition to being an important growth factor of goldfish macrophages, rgCSF-1 also plays a central role in the regulation of their pro-inflammatory responses.