Measuring the immune system of the three‐spined stickleback – investigating natural variation by quantifying immune expression in the laboratory and the wild

Abstract

Current understanding of the immune system comes primarily from laboratory‐based studies. There has been substantial interest in examining how it functions in the wild, but studies have been limited by a lack of appropriate assays and study species. The three‐spined stickleback (Gasterosteus aculeatus L.) provides an ideal system in which to advance the study of wild immunology, but requires the development of suitable immune assays. We demonstrate that meaningful variation in the immune response of stickleback can be measured using real‐time PCR to quantify the expression of eight genes, representing the innate response and Th1‐, Th2‐ and Treg‐type adaptive responses. Assays are validated by comparing the immune expression profiles of wild and laboratory‐raised stickleback, and by examining variation across populations on North Uist, Scotland. We also compare the immune response potential of laboratory‐raised individuals from two Icelandic populations by stimulating cells in culture. Immune profiles of wild fish differed from laboratory‐raised fish from the same parental population, with immune expression patterns in the wild converging relative to those in the laboratory. Innate measures differed between wild populations, whilst the adaptive response was associated with variation in age, relative size of fish, reproductive status and S. solidus infection levels. Laboratory‐raised individuals from different populations showed markedly different innate immune response potential. The ability to combine studies in the laboratory and in the wild underlines the potential of this toolkit to advance our understanding of the ecological and evolutionary relevance of immune system variation in a natural setting.

The right response at the right time: Exploring helminth immune modulation in sticklebacks by experimental coinfection

“…We monitored expression levels of the Treg related genes foxp3 , tgf‐β and il‐16 in all treatments over time. FoxP3 (Forkhead Box P3) is a characteristic transcription factor of regulatory T cells; TGF‐β (Transforming growth factor ß) is linked to development of Treg and Th17 cells (Robertson et al, ; Weaver, Harrington, Mangan, Gavrieli, & Murphy, ). TGF‐β is often classified as a proinflammatory agent despite having regulatory functions (Fischer, Koppang, & Nakanishi, ; Liu et al, ; Zhu, Nie, Zhu, Xiang, & Shao, ).…”

“…Expression levels of 23 G. aculeatus immune genes that may play key roles in S. solidus and D. pseudospathaceum infection were analyzed to characterize the molecular infection phenotypes. We chose genes that had been identified using transcriptome data (Haase et al, ; Huang et al, ) and quantitative real‐time PCR studies (Brunner et al, ; Robertson et al, ; Stutz, Schmerer, Coates, & Bolnick, ). Our set includes targets from innate and adaptive immunity as well as complement components.…”

Otolith development in wild populations of stickleback: Jones & Hynes method does not apply to most populations

“…The increasing interest in this fish demands a careful approach if reliable ages of wild‐caught individuals are to be inferred, since many patterns of interest to researchers are age‐related, including growth, senescence and other aspects of life history, as well as population dynamics, epidemiology and natural selection. To date, the main description of otolith reading in this species is Jones and Hynes (), but while still cited for ageing of G. aculeatus (Defaveri & Merila, ; MacColl et al ., ; Robertson et al ., ; Zeller et al ., ; Zimmerman, ), their main conclusions suggest a pattern for the deposition of opaque and translucent rings that contradicts that for most fishes and has substantial consequences for age estimation in this short‐lived species.…”

“…The determination of age in fishes by counting of annual rings on otoliths has been well established among researchers and fisheries managers for decades (Campana, 2005;Jones & Hynes, 1950). The method is still widely used (Koeda et al, 2016;Robertson et al, 2016;Uriarte et al, 2016) though more recent approaches for otolith analysis, such as daily increment quantification, microchemistry, carbon dating, plasma mass spectrometry and three dimensional x-ray scanning (Hippel et al, 2013;Jones & Chen, 2003;Mapp et al, 2016;Thorrold & Shuttleworth, 2000) are more powerful for age estimation.…”

“…Here we review the use of otoliths to age three-spined stickleback Gasterosteus aculeatus L. 1758, a small circumboreal fish of no significance to commercial fisheries, but which has increasingly become a model organism for the study of behaviour, ecology, parasitology, ecotoxicology, evolution and recently, and most prominently, evolutionary molecular genetics (Bell & Foster, 1994;Colosimo et al, 2005;Jones et al, 2012;Robertson et al, 2016). The increasing interest in this fish demands a careful approach if reliable ages of wildcaught individuals are to be inferred, since many patterns of interest to researchers are age-related, including growth, senescence and other aspects of life history, as well as population dynamics, epidemiology and natural selection.…”