Our research within immunoecology/eco-immunology has three focal areas, and hypotheses are tested on wild birds (in nature and captivity), and in laboratory-bred zebra finches.
Cost of disease and immune responses
The vertebrate immune system entails benefits (as defense against parasites), but it may also be costly to have and use. These costs can be direct induced by energy or nutrient limitations (constraining immune responses), or delayed induced by immunopatholgy (e.g. autoimmunity) or oxidative stress (‘too strong’ responses cause damage with severe consequences at later life stages). We use artificial infections to study:
- costs of (mild) disease – direct and delayed effects of infections
- energetic costs of innate and antibody-mediated immune responses
- fever responses in birds
- delayed costs of immune responses (and mechanisms mediating such costs).
Our work shows that direct costs of mild disease or immune responses per se seem surprisingly small, whereas long-term cost can be substantial even affecting survival. For example, we have found that in mild malaria, costs that are not directly visible can accumulate over time and eventually result in severe delayed costs shortening lifespan and reducing lifetime reproductive success. Oxidative stress and telomere shortening could be important mechanisms underlying these costs.
Constraints on immune function
A well-functioning immune system requires energy and nutrients, but also generates cytotoxic free radicals (for pathogen killing) that can harm healthy host cells. Hence, resources and risk of self-cell damage (immunopathology) may limit investment in immune defenses. We study how organisms trade-off these constraints against immune system functioning, in particular the importance of oxidative stress. Our previous work shows that variation in immunity can be explained by these trade-offs, and that trade-offs vary depending on life stage, sex or condition. We also study carry-over effects of heavy work load on immunity.
Maternal effects on offspring immune function
Maternal effects are ubiquitous and they can have both short- and long-term consequences for the offspring phenotype. We study how specific compounds (antibodies, hormones, antioxidants) – transferred from the mother to the offspring before birth – influence the immune system, and how this potentially affects fitness. Our work on a range of bird species (e.g. zebra finches, jackdaws) shows that maternal antibodies and steroid hormones can have profound impact on offspring immune responsiveness.