Reduced immune responsiveness contributes to winter energy conservation in an Arctic bird

• Published in: Journal of Experimental Biology
• Main Authors: Nord, Andreas, Hegemann, Arne, Folkow, Lars P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Company of Biologists Ltd 2020
• Subjects: Ecology; Immunology; Zoology; immune function; thermoregulation; bird; winter; season; Arctic; polar; immune response; anorexia; Svalbard
• Online Access: https://lup.lub.lu.se/record/17e57296-9ef7-49c9-a268-0052bf2037e8; https://doi.org/10.1242/jeb.219287

Animals in seasonal environments must prudently manage energyexpenditure to survive the winter. This may be achieved throughreductions in the allocation of energy for various purposes (e.g.thermoregulation, locomotion, etc.). We studied whether such tradeoffsalso include suppression of the innate immune response, bysubjecting captive male Svalbard ptarmigan (Lagopus mutahyperborea) to bacterial lipopolysaccharide (LPS) during exposureto either mild temperature (0°C) or cold snaps (acute exposure to−20°C), in constant winter darkness when birds were in energyconservingmode, and in constant daylight in spring. The innateimmune response was mostly unaffected by temperature. However,energy expenditure was below baseline when birds were immunechallenged in winter, but significantly above baseline in spring. Thissuggests that the energetic component of the innate immuneresponse was reduced in winter, possibly contributing to energyconservation. Immunological parameters decreased (agglutination,lysis, bacteriostatic capacity) or did not change (haptoglobin/PIT54)after the challenge, and behavioural modifications (anorexia, massloss) were lengthy (9 days). While we did not study the mechanismsexplaining these weak, or slow, responses, it is tempting to speculatethey may reflect the consequences of having evolved in anenvironment where pathogen transmission rate is presumably lowfor most of the year. This is an important consideration if climatechange and increased exploitation of the Arctic would alter pathogencommunities at a pace outwith counter-adaption in wildlife.