Development of Fish Peritoneal Macrophages as a Model for Higher Vertebrates in Immunotoxicological Studies: I. Characterization of Trout Macrophage Morphological, Functional, and Biochemical Properties

Development of Fish Peritoneal Macrophages as a Model for HigherVertebrates in Immunotoxicological Studies. I. Characterizationof Trout Macrophage Morphological, Functional, and BiochemicalProperties. ZELIKOFF, J. T., ENANE, N. A., BOWSER, D., SQUIBB,K. S., AND FRENKEL, K. (1991). Fundam. Appl. Toxicol. 16, 576–589.The immune defense mechanisms of fish are not as well characterizedas those of mammals but seem to be related and similarly competent.Because of this, there is an increased interest in the immuneresponses of fish as models for higher vertebrates in immunotoxicologicalstudies. Prior to such studies, baseline criteria for specificcomponents of the immune response needed to be established.For this study, we have examined trout macrophage morphologyusing light and scanning electron microscopy, phagocytic activity,random and stimulus-directed migration, and superoxide anionradical (^{dot}) production for resident and lipopolysacharide (LPS) or Aeromonas salmonicidae-elicited rainbowtrout (Oncorhynchus mykiss) peritoneal macrophages (M). Followingperitoneal lavage, >89% of the cells were M as determinedby differential counts and nonspecific esterase staining. Immunizationwith LPS and A. salmonicidae increased M number {small tilde}5and 13-fold, respectively, and overall size. Trout M were phagocyticallyactive engulfing serum opsonized latex particles and were mobile,migrating both randomly and in a directed fashion towards formyl-methionine-L-leucine-L-phenylalanine(FMLP) and trout serum-derived complement fragment C5a. Concentrationsof FMLP (100 nM) and C5a (0.01–1%) effective for attractingtrout M are the same as those used to attract rabbit M. Residenttrout M produced negligable quantities of-(^{dot}) following stimulation with 1 µg/ml phorbol myristate acetate;Aeromonas-elicited M produced (^{dot}) in a time-dependen manner which peaked after 60 min at 2.9 nmolper 2 ? 10₅ cells and then declined. The results of this studyprovide a data base for future toxicological studies with troutperitoneal M and indicate the usefulness of this system forimmunotoxicological studies.