Induction of inflammatory cytokines by extracellular products and LPS of the fish pathogen Aeromonas salmonicida ssp achromogenes in mice and mouse cell cultures

Balb/c mice, injected i.p. with extracellular products (ECP) of Aeromonas s almonicida subsp. achromogenes (Asa). displayed symptoms similar to toxic s hock syndrome. The LD50 observed was between 1.5 and 2.0 mug g(-1) and the mice died within 19 h. Four inflammatory cytokines were measured in mice re ceiving sublethal ECP doses. TNF-alpha and IL-6 showed a sharp peak in the serum while IL-1 beta and IL-2 were not detected. When peritoneal macrophag es were cultivated in the presence of ECR AsaP1 (a toxic caseinolytic metal lo-protease purified from ECP) or LPS, all cultures produced TNF-alpha, IL- 6 and IL-1 beta, The same antigens were mitogenic in spleen cell cultures. Furthermore. IL-2 production, which is a normal T-cell response to ConA sti mulation, was downregulated in spleen cell cultures from mice injected with ECR (C) 2001 Elsevier Science B.V. All rights reserved.