Sex‐Specific Variability in the Immune System across Life‐History Stages

Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
The American Naturalist (Impact Factor: 3.83). 10/2008; 172(3):E99-112. DOI: 10.1086/589521
Source: PubMed


Organisms theoretically manage their immune systems optimally across their life spans to maximize fitness. However, we lack information on (1) how the immune system is managed across life-history stages, (2) whether the sexes manage immunity differentially, and (3) whether immunity is repeatable within an individual. We present a within-individual, repeated-measures experiment examining life-history stage variation in the inflammatory immune response in the zebra finch (Taeniopygia guttata). In juveniles, age-dependent variation in immune response differed in a sex- and context-specific manner, resulting in no repeatability across stages. In adults, females displayed little stage-dependent variation in immune response when laying while receiving a high-quality (HQ) diet; however, laying while receiving a low-quality (LQ) diet significantly reduced both immune responses and reproductive outputs in a manner consistent with a facultative (resource-driven) effect of reproduction on immunity. Moreover, a reduced immune response in females who were raising offspring while receiving an HQ diet suggests a residual effect of the energetic costs of reproduction. Conversely, adult males displayed no variation in immune responses across stages, with high repeatability from the nonbreeding stage to the egg-laying stage, regardless of diet quality (HQ diet, r = 0.51; LQ diet, r = 0.42). Females displayed high repeatability when laying while receiving the HQ diet (r = 0.53); however, repeatability disappeared when individuals received the LQ diet. High-response females receiving the HQ diet had greater immune flexibility than did low-response females who were laying while receiving the LQ diet. Data are consistent with immunity being a highly plastic trait that is sex-specifically modulated in a context-dependent manner and suggest that immunity at one stage may provide limited information about immunity at future stages.

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    • "Sexual dimorphism in immunoresponsiveness is widespread among invertebrate and vertebrate taxa (e.g., McKean and Nunney 2005; Love et al. 2008; Nunn et al. 2009; Gershman et al. 2010; Aisenberg and Peretti 2011; Steiger et al. 2011). In adult vertebrates, males typically respond to immunological challenges less robustly than females (Møller et al. 1998; Klein 2000; Hasselquist 2007; Nunn et al. 2009; Pap et al. 2010; but see Tieleman et al. 2010), but when this difference in immune function manifests itself is less well-documented, particularly in birds. "
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