Ecoimmunology

Classical, or mainstream, immunology works hard to control variation (inbred/domestic model organisms, parasite-free environments, etc.) and asks questions about mechanisms and functionality of the immune system using a reductionist method. Comparative immunology investigates the major changes of the immune system among taxa. While ecoimmunology originated from these fields, it is distinguished by its focus to describe and explain natural variation in immune functions,[1] and, more specifically, why and how biotic and abiotic factors contribute to variation in immunity in animals. Study of the trade-offs between immunity and other physiological mechanisms are a central study topic within the field, but have been expanded to include roles in species and individual variation, sex, social aspects, and mating system differences, and progress is also being made to develop methods to explore this variation.[2] Many studies involve in vivo laboratory experiments, but there have been recent calls for immunologists to study immune variation more in wild animals in particular.[3] Multiple institutes engage in ecoimmunological research, such as the Center for Immunity, Infection and Evolution at the University of Edinburgh and the Max Planck Institute for Immunoecology and Migration. The US National Science Foundation has funded a Research Coordination Network) to bring methodological and conceptual unity to the field of ecoimmunology.

The immune system can be regarded as diary of exposition to viruses. Migration of animals lead to different exposure to animals as virus hosts. Combination of migration routes where individuals might be exposed to virus hosts can be used to cross-validate anti-gens and anti-bodies detected in the immune system of e.g. in migratory animals. For some viral infections you can detect in an early phase of the infection antibodies of the Immunglobulin class M (IgM) and later in the infection the detection of antibodies of the Immunglobulin class G (IgG) recommended. This basic example shows, how the integration of different approaches:

• spatial history and ecological history of virus exposition together with the local requirements and constraints to which the animals where exposed and
• temporal history when animals where exposed to viruses could lead to a deeper understanding of the natural variation in immune functions including chronic disease (as unsuccessful response of the immune system), partial immune response, ....

One of the field’s seminal papers, by Folstad and Karter,[4] was a response to Hamilton and Zuk’s famous paper on the handicap hypothesis for sexually selected traits.[5] Folstad and Karter proposed the immunocompetence handicap hypothesis, whereby testosterone acts as a mediator of immunosuppression and thus keeps sexually-selected traits honest.[4] Although there is only moderate observational or experimental evidence supporting this claim up until now, the paper itself was one of the first links to be made suggesting a cost to immunity requiring trade-offs between it and other physiological processes. In 1996, a foundational paper for the field invoked trade-offs, the allocation of limited resources among competing, costly physiological functions, as a prime cause of variation in immunity.[1] Evidence for these putative trade-offs has often proven to be elusive [6]

More recently, ecoimmunology has been the theme of three special issues in peer-reviewed journals, in Philosophical Transactions of the Royal Society B, in Functional Ecology, and in Physiological and Biochemical Zoology (see External links).

• NSF Research Collaborative Network: Refining and Diversifying Ecological Immunology
• Wild Immunology, University of Edinburgh
• Ecological Immunology Theme Issue of Philosophical Transactions of Royal Society B Table of Contents
• Special issue: Ecological Immunology, Functional Ecology Table of Contents
• Physiological and Biochemical Zoology Jan/Feb 2019 Special Issue on Ecoimmunology Table of Contents