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Androgens and the i...
Androgens and the immunocompetence handicap hypothesis: Unraveling direct and indirect pathways of immunosuppression in song sparrows
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Owen-Ashley, N T (författare)
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- Hasselquist, Dennis (författare)
- Lund University,Lunds universitet,MEMEG,Biologiska institutionen,Naturvetenskapliga fakulteten,Department of Biology,Faculty of Science
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Wingfield, J C (författare)
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(creator_code:org_t)
- 2004
- 2004
- Engelska.
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Ingår i: American Naturalist. - 0003-0147. ; 164:4, s. 490-505
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Abstract
Ämnesord
Stäng
- The immunocompetence handicap hypothesis proposes that testosterone (T)-dependent sexual signals are honest indicators of male health or genetic quality because only high-quality males are able to withstand the obligate effects of T-induced immunosuppression. In birds, the basic assumption that T suppresses immune function is equivocal, and the physiological mechanisms underlying T-induced immunosuppression remain to be investigated. We explored the proximate pathways of T-induced immunosuppression in song sparrows (Melospiza melodia) by treating captive nonbreeding males with different androgens and measuring several components of acquired immune function. Males implanted with T suppressed cell-mediated and humoral immune responses compared to males implanted with 5proportional to-dihydrotestosterone (DHT), dehydroepiandrosterone, or control ( empty) implants. Furthermore, T treatment increased plasma levels of corticosterone and decreased body mass and fat stores in relation to other treatments. The failure of DHT to depress immune function suggests that T-induced immunosuppression does not occur through a direct pathway because both T and DHT bind to androgen receptors on target cells. Instead, we outline indirect pathways that are likely responsible for suppression of the avian immune system that include stress-induced immunosuppression, aromatization to estrogen, and alterations in energy allocation that constrain expenditures toward immune system activation.
Ämnesord
- NATURVETENSKAP -- Biologi (hsv//swe)
- NATURAL SCIENCES -- Biological Sciences (hsv//eng)
Nyckelord
- immunosuppression
- song sparrow
- testosterone
- corticosterone
- androgens
- immunocompetence
Publikations- och innehållstyp
- for (ämneskategori)
- ref (ämneskategori)
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