Beyond phytohaemagglutinin: assessing vertebrate immune function across ecological contexts

Abstract

Summary 1.Over the past decade, there has been a substantial increase in interest in the immune system and the role it plays in the regulation of disease susceptibility, giving rise to the field of eco-immunology. 2. Eco-immunology aims to understand changes in host immune responses in the broader framework of an organism's evolutionary, ecological and life-history contexts. 3. The immune system, however, is complex and multifaceted and can be intimidating for the nonimmunologist interested in incorporating immunological questions into their research. Which immune responses should one measure and what is the biological significance of these measures? 4. The focus of this review is to describe a wide range of eco-immunology techniques, from the simple to the sophisticated, with the goal of providing researchers with a range of options to consider incorporating in their own research programs. 5. These techniques were chosen because they provide relatively straightforward, biologically meaningful assessments of immune function, many of which can be performed across a range of ecological contexts (i.e. field vs. laboratory) and in a wide range of vertebrate animals without relying on species-specific reagents. 6. By incorporating assessments of immune function into their specific research questions, animal ecologists will gain a more comprehensive understanding of organism-environment interactions.

Cellular and humoral immunity in a wild mammal: Variation with age & sex and association with overwinter survival

“…Other vertebrate studies measuring many immune markers have reported generally weak correlations and complex patterns of association between these measures and resistance or health outcomes (Banos et al., 2013; Buehler, Versteegh, Matson, & Tieleman, 2011; Flori et al., 2011; Keil, Luebke, & Pruett, 2001; Matson, Cohen, Klasing, Ricklefs, & Scheuerlein, 2006). This suggests that one or a few measures of immunity are unlikely to capture broadscale variation in immune responsiveness and the ability to resist parasites, and raises the important question of which of the potentially huge range of immune markers are likely to be most relevant for ecological and evolutionary studies (Boughton et al., 2011; Demas et al., 2011). We found that the only immune marker to predict survival over the subsequent winter on St Kilda was the abundance of IgG antibodies against T. circumcincta .…”

“…While nematode‐specific antibodies in blood correlate with mucosal antibody activity at the site of infection in sheep (Prada Jiménez de Cisneros, Matthews, Mair, Stefan, & Stear, 2014), it is not clear whether the proportions of different leukocytes measured here reflect only the available immune cell selection pool rather than the mucosal effector population. The well‐established complexity of the vertebrate immune system, which is clearly illustrated by the weak age‐independent correlations among our 11 immune markers, represents a major challenge for eco‐immunologists seeking to identify a handful of salient immune measurements to study in the field (Boughton, Joop & Armitage 2011; Demas et al, 2011). Our results suggest that antibodies specific to prevalent parasites or pathogens may offer the most insight in terms of their relationship with health and fitness.…”

“…The innate immune system, which is the older in evolutionary terms, refers to nonspecific defense mechanisms which become activated immediately or within hours of antigen encounter. These defense mechanisms include anatomical barriers and behaviors to avoid infection, humoral factors such as complement and acute phase proteins, and a variety of functionally diverse white blood cells including macrophages, neutrophils, and eosinophils (Demas et al., 2011). The adaptive immune system refers to antigen‐specific immunity and is more complex than innate immunity and slower to develop.…”

Short‐term resource allocation during extensive athletic competition

“…While past studies predominantly consider trade‐offs acting on a long‐term evolutionary scale, the present study employs the conceptual framework provided by life history theory as a reference to consider acute trade‐offs. It was hypothesized that markers of investment in reproductive function (Demas, Zysling, Beechler, Muehlenbein, & French, 2011) will decrease in magnitude, allowing for an increase in markers indicative of investment in short‐term survival. This is due to the high costs of male mating effort (Ellison, 2003) and the suggestion that survival may be prioritized over other processes (Bronson, 1991).…”

Immune Response to Newcastle Disease Virus Vaccination in a Wild Passerine

“…However, the study of adaptive responses to specific wild pathogens can yield relevant information on epidemiologic and evolutionary issues concerning host-pathogen dynamics (Demas et al, 2011).…”