Pollution-Related Decrease in the T-Cell Immune Response in a Wild Bird Species

Impact of exposure to pollutants on fitness-linked functions in wild animals is a great concern in ecotoxicology. In this study, we aimed to assess how prior exposure to chemical pollution in an industrialized area close to Gabès city in southern Tunisia (the Gabès–Ghannouche factory complex) might affect the T-cell mediated immunocompetence in a common wild bird species, namely the Hybrid sparrow (Passer domesticus x hispaniolensis). Using the phytohaemagglutinin (PHA) test, we compared the strength of T-cell mediated response (CMI) in sparrows living in the factory complex (polluted site) with that in sparrows living far from, in an industry-free area (reference site). Sparrows from the polluted site showed lower levels of CMI compared to those from the reference site, suggesting that chronic exposure to chemical pollution induced a reduced T-cell mediated immunocompetence. This finding is probably due to a trade-off in resource allocation between anti-oxydative and immune functions and/or to the ability of pollutants, notably trace elements, to act as powerful endocrine distributors. Further investigations including additional measures of immune function are needed to better understand this issue.