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 demonstrat ed the immunotoxicity of organochlorines. This study confirmed that associa tions between organochlorines and suppressed T cell function and enhanced a ntibody production in young Caspian terns from the Great Lakes, first obser ved in the early 1990s, continued into the late 1990s. These associations w ere based on measurement of organochlorines in plasma of individuals and po oled egg samples. During 1997-99, immune function, hematological variables, and organochlorine contamination were measured in prefledgling Caspian ter ns at two Lake Huron colonies: Channel Shelter Island (Confined Disposal Fa cility) at the mouth of the Saginaw River in southern Saginaw Bay and Elm I sland in the North Channel. Elevated organochlorine exposure, reproductive effects, and decreased recruitment have been documented previously in the S aginaw Bay colony. Concentrations of polychlorinated biphenyls (PCBs) in eg gs and plasma and 1,1-dichloro-2,2-bis(p)chlorophenyl)ethylene (DDE) in pla sma were consistently higher in Saginaw Bay compared to the North Channel. The mean phytohemagglutinin (PHA) skin test, a measure of T lymphocyte func tion, was 42% lower in Saginaw Bay. Regression analyses showed strong negat ive associations between the PHA response and plasma PCBs and, to a slightl y lesser degree, DDE. Despite interyear differences, total antibody titers following immunization with sheep red blood cells were higher in Saginaw Ba y than the North Channel. Titers were positively associated with plasma PCB s and DDE. Plasma PCBs and DDE were negatively correlated with the percenta ge of monocytes and positively correlated with the percentage of basophils.