Immunity in a variable world

Abstract

Immune function is likely to be a critical determinant of an organism's fitness, yet most natural animal and plant populations exhibit tremendous genetic variation for immune traits. Accumulating evidence suggests that environmental heterogeneity may retard the long-term efficiency of natural selection and even maintain polymorphism, provided alternative host genotypes are favoured under different environmental conditions. 'Environment' in this context refers to abiotic factors such as ambient temperature or availability of nutrient resources, genetic diversity of pathogens or competing physiological demands on the host. These factors are generally controlled in laboratory experiments measuring immune performance, but variation in them is likely to be very important in the evolution of resistance to infection. Here, we review some of the literature emphasizing the complexity of natural selection on immunity. Our aim is to describe how environmental and genetic heterogeneities, often excluded from experimentation as 'noise', may determine the evolutionary potential of populations or the potential for interacting species to coevolve.

Integrating nutrition and immunology: A new frontier

“…Alternatively, the gut microbiota can indirectly affect the development and persistence of parasites by inducing the host's immune system (Buchon et al, 2009;Douglas, 2010;Feldhaar and Gross, 2008;Kau et al, 2011;Lazzaro and Little, 2009;Ryu et al, 2010;Ryu et al, 2008;Wen et al, 2008). For instance, in mosquitoes, commensals can modulate Plasmodium infection (Cirimotich et al, 2011;Gonzalez-Ceron et al, 2003;Meister et al, 2009;Pumpuni et al, 1996).…”

“…It has long been recognized that the immune response is modulated not only by host (and parasite) genetics, but also by host nutrition, (Lazzaro and Little, 2009;Schmid-Hempel, 2011), yet there remain important gaps in our knowledge. Gaining a fuller understanding of the interface between nutrition and immunity is particularly important for three reasons.…”

“…Gaining a fuller understanding of the interface between nutrition and immunity is particularly important for three reasons. First, immune function is affected by host nutrition, which may greatly affect the outcome of infection (Lazzaro and Little, 2009;Schmid-Hempel, 2011). Host nutrition influences both constitutive and inducible immune function, with consequences for morbidity and mortality (Cunningham-Rundles et al, 2005;Klasing, 2007) (Adams and Hewison, 2008;Amar et al, 2007;Calder, 2006;Cohen et al, 2008;Kelley and Bendich, 1996;Klasing, 2007;Kolb, 1997;Kristan, 2007;Samartin and Chandra, 2000;Sorci and Faivre, 2009).…”

Temporal variation in temperature determines disease spread and maintenance inParameciummicrocosm populations

“…Short-term correlative studies have linked mean temperatures in the field to differences in parasite incidence and disease across years [7,8]. Similarly, experimental studies have considered how differences in environmental means affect outcomes for host-parasite dynamics [4,9,10]. These studies demonstrate the sensitivity of the host and parasite to mean values of several environmental parameters.…”

Cold‐seeking behaviour mitigates reproductive losses from fungal infection in Drosophila

“…Together, these results suggest that if we only conduct our experiments under a single thermal condition, which does not represent the highly variable environment experienced by organisms under natural conditions, we may not be able to accurately assess the costs and benefits of immunity. In particular, phenotypes which result from genetic and environmental interactions may be missed (Moret & Schmid‐Hempel 2004; Lazzaro & Little 2009; Paaijmans et al . 2013).…”