Meeting Abstract
Mounting an immune response destroys pathogens, but this response comes at a physiological cost, including the production of oxidative damage. However, many investigations into the effects of immune challenges employ a single high dose, meaning that the consequences of more mild immune challenges, which may be a better representation of naturally occurring immune challenges, are poorly resolved. We used nestling tree swallows to test how degree of immunological challenge modifies oxidative physiology and body mass, and how these metrics interact with ectoparasite load. Thus, we injected 14-day-old nestlings with either 0, 0.01, 0.1, or 1 mg lipopolysaccharide (LPS) per kg body mass, collected a blood sample 24-h later, recorded body mass, and collected nests for ectoparasite identification. From the blood sample, we quantified oxidative damage via two methodologies: TBARS, which quantifies lipid peroxidation, and d-ROMs, which quantifies derivatives of reactive oxygen metabolites. We found that nestlings injected with 1.0 mg LPS/kg body mass, which is a common dosage in ecoimmunological studies, lost significantly more body mass than individuals in other treatment groups. While treatment had no effect on TBARS, there was a dose-dependent relationship between concentration of LPS injection and d-ROMs, with higher amounts of LPS resulting in more oxidative damage. We conclude that while low-intensity immune challenges may not affect body mass maintenance, these challenges still result in detectable increases of oxidative damage. Also, nestlings subjected to blowflies and mites had higher d-ROMs values, underscoring a link between this metric of oxidative stress and immune challenges.
