Ecoimmunology

Ecoimmunology or Ecological Immunology is the study of the causes and consequences of variation in immunity. The field of ecoimmunology seeks to give an ultimate perspective for proximate mechanisms of immunology. This approach places immunology in evolutionary and ecological contexts across all levels of biological organization.

Classical, or mainstream, immunology works hard to control variation (inbred/domestic model organisms, parasite-free environments, etc.) and asks questions about the mechanisms and functionality of the immune system using a reductionist method. While ecoimmunology originated from these fields, it is distinguished by its focus to explain natural variation in immune functions.

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 causes and consequences of immune variation have larger implications for public health, conservation, wildlife management, and agriculture.

History

Ecological Immunology is a discipline that uses ecological perspectives to understand variation in immune function. Specifically, to explain how abiotic and biotic factors influence the variation in immune function. Articles began discussing ecological contexts and of immune variation in the 1970s but matured into a discipline in the 1990s. Ecoimmunology is an integrative field that combines approaches from evolutionary biology, ecology, neurobiology, and endocrinology.

Seminal papers

Seminal papers in the field include Sheldon & Verhulst's which proposed concepts from Life history theory, trade-offs and allocation of resources between competing costly physiological functions, are a cause of variation in immunity One of the field's seminal papers, by Folstad and Karter, was a response to Hamilton and Zuk's famous paper on the handicap hypothesis for sexually selected traits. Folstad and Karter proposed the immunocompetence handicap hypothesis, whereby testosterone acts as a mediator of immunosuppression and thus keeps sexually-selected traits honest. 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.

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).

Known factors that influence immune variation

Intraspecific constraints

Organisms allocate energy between competing processes including self-maintenance, reproduction, or growth. Energy availability is limited, and the resources used for one of the competing metabolic tasks (i.e., growth, immune response) cannot be directed towards another. The cost of immunity is central to the understanding of ecoimmunology. Natural selection should favor the optimal immune response that maximizes total lifetime reproductive output. The costs of immunity to parasites occur at the individual and the evolutionary scale. Trade-offs between bodily demands are titrated in relation to the local and social ecology.

Innate versus acquired

One axis on which these trade-offs occur is the trade-off between innate