Superoxide production in phagocytes obtained from Mycobacterium marinum-stimulated goldfish (Carassius auratus) that were exposed to copper

Objective-To investigate the effects of copper exposure and recovery from c opper toxicosis on the nonspecific immune response in Mycobacterium marinum -inoculated goldfish. Animals-Goldfish (Carassius auratus) with a mean weig ht of 33.5 g. Procedure-Superoxide (O-2-) production was measured in fish 2 to 6 weeks af ter injection with phosphate-buffered saline (PBS) solution or M marinum (1 0(2) to 10(7) colony-forming units [CFU]/fish). Then, paired groups of fish were injected with PBS solution or 10(4) CFU Of M marinum and exposed to c opper(100 mu g/L) for 7 days or for 4 days with 3 days of recovery. One pai red group not exposed 14 days later to copper served as control fish. Phago cyte production of O-2- was measured by use of the nitroblue tetrazolium re duction assay, inflammation and bacterial colony counts were determined by use of routine histologic and microbiologic procedures. Results-Superoxide production achieved a maximal response 2 to 4 weeks afte r M marinum inoculation. Compared with control fish, O-2- production increa sed in the groups exposed to copper but then decreased in the exposed group s that were allowed to recover. Superoxide response and peritoneal inflamma tion were greater in M marinum-inoculated groups than in noninoculated grou ps. Conclusions-Copper exposure and inoculation with M marinum increased O-2- p roduction, whereas recovery after exposure decreased O-2- production, even in fish that were immunostimulated by M marinum. Clinical Relevance-When the antimicrobial oxidative response is suppressed after copper exposure, steps should be taken to avoid imposing additional s tress and minimize the possibility of resurgent or secondary pathogenic inf ections.