title: Sources of variation in innate immunity in great tit nestlings living along a metal pollution gradient: an individual-based approach.
abstract: Excessive deposition of metals in the environment is a well-known example of pollution worldwide. Chronic exposure of organisms to metals can have a detrimental effect on reproduction, behavior, health and survival, due to the negative effects on components of the immune system. However, little is known about the effects of chronic sublethal metal exposure on immunity, especially for wildlife. In our study, we examined the constitutive innate immunity of great tit (Parus major) nestlings (N=234) living in four populations along a metal pollution gradient. For each nestling, we determined the individual metal concentrations (lead, cadmium, arsenic) present in the red blood cells and measured four different innate immune parameters (agglutination, lysis, haptoglobin concentrations and nitric oxide concentrations) to investigate the relationship between metal exposure and immunological condition. While we found significant differences in endogenous metal concentrations among populations with the highest concentrations closest to the pollution source, we did not observe corresponding patterns in our immune measures. However, when evaluating relationships between metal concentrations and immune parameters at the individual level, we found negative effects of lead and, to a lesser extent, arsenic and cadmium on lysis. In addition, high arsenic concentrations appear to elicit inflammation, as reflected by elevated haptoglobin concentrations. Thus despite the lack of a geographic association between pollution and immunity, this type of association was present at the individual level at a very early life stage. The high variation in metal concentrations and immune measures observed within populations indicates a high level of heterogeneity along an existing pollution gradient. Interestingly, we also found substantial within nest variation, for which the sources remain unclear, and which highlights the need of an individual-based approach.
authors.affiliation: Department of Biology - Ethology, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium. Electronic address: anke.vermeulen@uantwerpen.be.
authors.forename: Anke
authors.initials: A
authors.lastname: Vermeulen
authors.affiliation: Department of Biology - Ethology, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium. Electronic address: wendt.mueller@uantwerpen.be.
authors.forename: Wendt
authors.initials: W
authors.lastname: Müller
authors.affiliation: Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands; The Resource Ecology Group, Department of Environmental Sciences, Wageningen University, Droevendaalsesteeg 3a, 6708PB Wageningen, The Netherlands. Electronic address: k.d.matson@rug.nl.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Matson
authors.affiliation: Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands. Electronic address: b.i.tieleman@rug.nl.
authors.forename: B Irene
authors.initials: BI
authors.lastname: Tieleman
authors.affiliation: Department of Biology - SPHERE, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerpen, Belgium. Electronic address: lieven.bervoets@uantwerpen.be.
authors.forename: Lieven
authors.initials: L
authors.lastname: Bervoets
authors.affiliation: Department of Biology - Ethology, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium. Electronic address: marcel.eens@uantwerpen.be.
authors.forename: Marcel
authors.initials: M
authors.lastname: Eens
mesh_terms: D000818:Animals; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000032:analysis / Q000633:toxicity*; D004787:Environmental Pollution / Q000706:statistics & numerical data; D007113:Immunity, Innate / Q000187:drug effects*; D008669:Metallurgy; D008670:Metals / Q000032:analysis / Q000633:toxicity*; D020308:Songbirds
chemical_list: D004785:Environmental Pollutants; D008670:Metals
keywords: Acute phase proteins; Complement; Constitutive innate immunity; Natural antibodies; Nestlings; Nitric oxide