Abstract
Innate immune function is potentially energetically expensive. We tested the hypothesis, posited by life history theory, that trade‐offs exist among energetically expensive activities (e.g., innate immune function and metabolic rate). We assessed innate immune function by injecting mice with lipopolysaccharide (LPS), and we measured basal metabolic rates (BMR) and maximal metabolic rates (MMR). Mice were artificially selected either for high MMR (MAX lines) or for high MMR and low BMR (COR lines). All selection was on mass‐independent metabolism. After 7 generations of selection, mass‐adjusted BMR was highest in MAX mice, intermediate in COR mice, and lowest in non‐selected controls (CONT) (0.61, 0.57, and 0.59 ml O2/min, respectively). Immune challenged (i.e., LPS injected) mice had higher BMR than mice injected with saline (0.88 and 0.80 ml O2/min, respectively), and during the immune challenge BMR was most elevated in COR mice. COR mice also had the greatest aerobic scope (MMR‐BMR). Collectively, these results suggest a possible trade‐off between cost of mounting an innate immune response and ability to elevate MR during aerobic activity (i.e., aerobic scope). Support: NSF IOS 0344994.