Multivariate immune defences and fitness in the wild: complex but ecologically important associations among plasma antibodies, health and survival

Research on St Kilda's unmanaged Soay sheep population reveals that helminth-specific immunity, specifically anti-nematode immunoglobulin (Ig) G antibodies measured during summer, is strongly linked to over-winter survival, offering rare evidence of a fitness benefit under natural conditions. The study analyzed 11 different antibody types in adult female sheep, finding weak but generally positive correlations among them. Eight antibody measures independently predicted body mass, strongyle parasite egg count, or survival, highlighting the complex and multivariate nature of immune responses in wild systems. This work underscores the ecological and evolutionary significance of immune phenotypes, challenging simplistic views of immunity and emphasizing its multifaceted role in organismal health and fitness.

Nussey, D. H., Watt, K. A., Clark, A., Pilkington, J. G., Pemberton, J. M., Graham, A. L., & McNeilly, T. N. (2014). Multivariate immune defences and fitness in the wild: complex but ecologically important associations among plasma antibodies, health and survival. Proceedings of the Royal Society B: Biological Sciences, 281(1779), 20132931. https://doi.org/10.1098/rspb.2013.2931