Although the immune system is central to survival, animals show great variation in their immune investment. This is related to trade-offs resulting from costs of immune system maintenance and activation and competing demands (investment in sexual signals, parental care). I study how these trade-offs are affected by individual quality, hormonal status, diet quality and environmental factors.

Personality and innate immune defenses in a wild bird: evidence for the pace-of-life hypothesis.
Jacques-Hamilton R, ML Hall, WA Buttemer, KD Matson, A Gonҫalves da Silva, RA Mulder, A Peters. 2017. Personality and innate immune defenses in a wild bird: evidence for the pace-of-life hypothesis. Horm Behav 88:31-40

We showed that superb fairy-wrens that are more inclined to engage in risky behaviours, have lower levels of natural antibodies, but that this is not related to their sensitivity to stress.

The carotenoid conundrum: improved nutrition boosts plasma carotenoid levels but not immune benefits of carotenoid supplementation.
Peters, A, S. Magdeburg & K. Delhey. 2011. The carotenoid conundrum: improved nutrition boosts plasma carotenoid levels but not immune benefits of carotenoid supplementation. Oecologia 166(1): 35-43

In a 2 x 2 experiment manipulating carotenoid content and general quality of the diet we found that carotenoid levels in circulation were strongly enhanced by an improved diet, but that the beneficial effects of carotenoids were determined by dietary content only.

Is testosterone immunosuppressive in a condition-dependent manner? An experimental test in blue tits.
Roberts ML & A Peters. 2009. Is testosterone immunosuppressive in a condition-dependent manner? An experimental test in blue tits. J Exp Biol 212:1811-1818

The effect of flavonoids on humoral immune response and food selection in a frugivorous bird.
Catoni C, HM Schaefer & A Peters. 2008 Fruit for health: The effect of flavonoids on humoral immune response and food selection in a frugivorous bird. Funct Ecol 22(4):649-654

This provides the first evidence that a wild bird selects food containing flavonoids (coloured dietary antioxidants) and that selection for flavonoids improves immune responsiveness. Birds supplemented with flavonoids were almost twice as likely to mount an immune response.

Tradeoffs between immune investment and sexual signaling in male mallards.
Peters A, K Delhey, AG Denk & B Kempenaers. 2004. Tradeoffs between immune investment and sexual signaling in male mallards. Am Nat 164(1): 51-59

This paper describes consequences of immune system activation on sexual signaling, and physiological condition, examining a suite of changes induced by the immune response, rather than components in isolation.

Testosterone treatment is immunosuppressive in superb fairy-wrens, yet free-living males with high testosterone are more immunocompetent.
Peters A. 2000. Testosterone treatment is immunosuppressive in superb fairy-wrens, yet free-living males with high testosterone are more immunocompetent. Proc R Soc Lond B 267(1446): 883-889

This paper presented a comprehensive test of the assumptions and predictions of the immunocompetence handicap hypothesis on life-history consequences of immune suppression by testosterone.