Association between chronic organochlorine exposure and immunotoxicity in the round stingray (Urobatis halleri)

- Round stingrays chronically exposed to organochlorines had higher cell concentration in whole blood than control rays.
- PCB load explained higher % phagocytosis in the blood of contaminated rays.
- PCB and pesticide loads predicted increased splenic phagocytic activity in chronically contaminated rays.
- Strong evidence of organochlorine correlated immunostimulation in elasmobranchs is provided.

Chronic organochlorine (OC) exposure has been shown to cause immune impairment in numerous vertebrate species. To determine if elasmobranchs exhibited compromised immunity due to high OC contamination along the coastal mainland of southern California, innate immune function was compared in round stingrays (Urobatis halleri) collected from the mainland and Santa Catalina Island. Proliferation and phagocytosis of peripheral blood, splenic, and epigonal leukocytes were assessed. Percent phagocytosis and mean fluorescence intensity (MFI) were evaluated by quantifying % leukocytes positive for, and relative amounts of ingested fluorescent E. coli BioParticles. Total cell proliferation differed between sites, with mainland rays having a higher cell concentration in whole blood. ∑PCB load explained significantly higher % phagocytosis in blood of mainland rays, while ∑PCB and ∑pesticide loads described increased splenic % phagocytosis and MFI in the mainland population. Data provides evidence of strong OC-correlated immunostimulation; however, other site-specific environmental variables may be contributing to the observed effects.

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