Associations between altered immune function and organochlorine contamination in young Caspian terns (Sterna caspia) from Lake Huron, 1997-1999.

Previous studies of laboratory animals and wildlife species have demonstrated the immunotoxicity of organochlorines. This study confirmed that associations between organochlorines and suppressed T cell function and enhanced antibody production in young Caspian terns from the Great Lakes, first observed in the early 1990s, continued into the late 1990s. These associations were based on measurement of organochlorines in plasma of individuals and pooled egg samples. During 1997-99, immune function, hematological variables, and organochlorine contamination were measured in prefledgling Caspian terns at two Lake Huron colonies: Channel Shelter Island (Confined Disposal Facility) at the mouth of the Saginaw River in southern Saginaw Bay and Elm Island in the North Channel. Elevated organochlorine exposure, reproductive effects, and decreased recruitment have been documented previously in the Saginaw Bay colony. Concentrations of polychlorinated biphenyls (PCBs) in eggs and plasma and 1,1-dichloro-2,2-bis(p)chlorophenyl)ethylene (DDE) in plasma were consistently higher in Saginaw Bay compared to the North Channel. The mean phytohemagglutinin (PHA) skin test, a measure of T lymphocyte function, was 42% lower in Saginaw Bay. Regression analyses showed strong negative associations between the PHA response and plasma PCBs and, to a slightly lesser degree, DDE. Despite interyear differences, total antibody titers following immunization with sheep red blood cells were higher in Saginaw Bay than the North Channel. Titers were positively associated with plasma PCBs and DDE. Plasma PCBs and DDE were negatively correlated with the percentage of monocytes and positively correlated with the percentage of basophils.