Abstract
Life history theory predicts resource allocation trade-offs between competing functions and processes. We test the hypothesis that relative investment towards innate versus acquired immunity in humans is subject to such trade-offs and that three types of early developmental exposures are particularly salient in shaping adult immunophenotype: (i) pathogen exposure, (ii) nutritional resources; and (iii) extrinsic mortality cues. We quantified one aspect each of innate and acquired immune function, via C-reactive protein and Epstein-Barr virus antibodies, respectively, in a sample of 1248 men and women from the Philippines (ca. 21.5 years old). Early developmental exposures were assessed via long-term data collected prospectively since participants' birth (1983-4). We calculated a standardized ratio to assess relative bias towards acquired versus innate immune function and examined its relationship to a suite of predictors via multiple regression. In partial support of our predictions, some of the measures of higher pathogen exposure, greater availability of nutritional resources, and lower extrinsic mortality cues in early life were associated with a bias toward acquired immunity in both men and women. The immune profile of women, in particular, appeared to be more sensitive to early life pathogen exposures than those of men. Finally, contrary to prediction, women exhibited a greater relative investment toward innate, not acquired, immunity. Early environments can exert considerable influence on the development of immunity. They affect trade-offs between innate and acquired immunity, which show adaptive plasticity and may differ in their influence in men and women.
Highlights
Background and objectivesLife history theory predicts resource allocation trade-offs between competing functions and processes
Building on past work in other species [14, 15, 30], we recently proposed that the balance of investment in innate versus acquired immune defenses in humans will depend upon three axes of ecological variation experienced early in development: infectious exposure, nutritional resources, and extrinsic mortality cues [31]
Using two markers of immune function, C-reactive protein (CRP) and Epstein–Barr virus (EBV) antibodies, we assess relative investment toward innate and acquired immune defenses, respectively, in a large cohort of ca. 21.5-year olds. With data on their early-life environments, we examine whether their adult immunophenotype exhibits patterns consistent with the hypothesis of early developmental plasticity and trade-offs across branches of immune function [31]
Summary
Background and objectivesLife history theory predicts resource allocation trade-offs between competing functions and processes. A life history approach views biology through the lens of the lifecycle and focuses attention on development and the plasticity involved in calibrating the phenotype of the individual, in response to inputs from the environment early in life [11] These threads converge within the emerging discipline of ecological immunology (ecoimmunology), which places particular emphasis on how ecological factors affect an individual’s immunophenotype and places an organism’s investment in immune defenses within the context of local environmental conditions [12, 13]. Such an ecoevolutionary approach aims to explain substantial species- and individual-level variation in immune function and to provide a mechanistic understanding of the life-history trade-offs individuals may incur over their lifetime. The explanatory frameworks developed within the literature on other vertebrates, have not been explicitly tested on humans
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