Nitroblue tetrazolium dye reduction by earthworm (lumbricus terrestris) coelomocytes: An enzyme assay for nonspecific immunotoxicity of xenobiotics

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Abstract
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 potential of human leukocytes to oxidatively kill phagocytosed microorganisms. Coelomocyte NBT reduction, which exhibited time–response patterns similar to those of human and murine neutrophils and murine macrophages, 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 RDFF:commercial soil mixtures decreased significantly with increasing sublethal RDFF concentrations of 10, 30, 50, and 70%. Compared to soil‐exposed controls, dye reduction was significantly suppressed in all but the 10% RDFF group: 40, 59, and 64% of controls, respectively. Differences were significant among experimentals, except between 50 and 70% RDFF. Tissue levels of Cu and Pb accorded with RDFF exposure concentrations in which suppression of NBT reduction occurred. NBT reduction was not significantly suppressed in coelomocytes from earthworms exposed to 70% fly ash that had been acid‐washed to remove metals.