Effect of Exposure to Various Sites within Hamilton Harbour on Oncorhynchus mykiss Pronephros Macrophage Function and B Cell Numbers

Our objective was to assess whether or not exposure to sites within Hamilton Harbour known to be highly contaminated with polycyclic aromatic hydrocarbons (PAHs), heavy metals, and sewage treatment plant (STP) effluent could affect macrophage function and B-cell numbers in fish. Caged rainbow trout ( Oncorhynchus mykiss) were sampled after 7, 14, and 21 days of exposure to five harbor sites, plus a Lake Ontario reference site. Four of the harbor sites were selected for their proximity to either highly contaminated sediments or industrial and municipal discharges; the fifth site was selected as a harbor reference site. Pronephros leukocytes from fish at the six sites were evaluated for phagocytic activity, oxidative burst, and the number of surface immunoglobulin-positive B cells. Although none of the immune parameters and B-cell numbers measured from fish that were caged at the contaminated harbor sites were significantly different from the harbor reference site, they were significantly different from the Lake Ontario reference site. Fish showed a greater reduction in pronephros leukocyte phagocytic activity over the course of the study when compared to the Lake Ontario reference fish; pronephros leukocyte oxidative burst was also reduced at two of the harbor sites. B cell counts did not change throughout the duration of the study, although overall counts were lower at two of the harbor sites when compared to the Lake Ontario site. The results indicate that macrophage function and B-cell numbers were altered in fish by exposure to various sites in Hamilton Harbour. The possible immunomodulatory roles of chemical and physical parameters at those sites are discussed.