| Earthworm (Lumbricus terrestris) coelomic leukocytes, or coelomocytes, were shown to have sufficient ability to reduce nitroblue tetrazolium dye (NBT) for potential use as a surrogate biomarker to assess nonspecific immunotoxicity of environmental xenobiotics. NBT reduction is used clinically to evaluate the potential of human leukocytes to oxidatively kill phagocytosed microorganisms. Coelomocyte NBT reduction, which exhibited time-response patterns similar to those of human and murine leukocytes, was sensitive to Cu and/or Pb contaminants in refuse-derived fuel fly ash (RDFF). NBT reduction by coelomocytes from earthworms exposed for 5 d to 10, 30, 50 or 70% RDFF:commercial soil mixtures decreased significantly with increasing sublethal RDFF concentrations when compared to soil-exposed controls. Suppression occurred in all but the 10% group at 40, 59 and 64% of controls, respectively. Tissue levels of Cu;Lysozyme-like activity in earthworm coelomic fluid and coelomocytes was also shown to have potential use as a surrogate biomarker to assess innate immunotoxicity of terrestrial wastes. Lysozyme is a phylogenetically-conserved enzyme capable of bactericidal activity via action on peptidoglycan of Gram-positive bacterial cell walls. Earthworm lysozyme-like activity in both coelomic fluid and coelomocytes, similar to that in mammalian serum and leukocytes, was reduced significantly after exposure of earthworms for 5 d to CuSO;Results herein suggest that both NBT reduction and lysozyme activity assay systems are useful for determining the immunotoxicity of xenobiotics via their effects on antimicrobial defense mechanisms. |
