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Androgens and the immunocompetence handicap hypothesis: Unraveling direct and indirect pathways of immunosuppression in song sparrows

In English

Författare

Summary, in English

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.

Publiceringsår

2004

Språk

Engelska

Sidor

490-505

Publikation/Tidskrift/Serie

American Naturalist

Volym

164

Issue

4

Dokumenttyp

Artikel i tidskrift

Förlag

University of Chicago Press

Ämne

  • Biological Sciences

Nyckelord

  • immunosuppression
  • song sparrow
  • testosterone
  • corticosterone
  • androgens
  • immunocompetence

Status

Published

Forskningsgrupp

  • Molecular Ecology and Evolution Lab

ISBN/ISSN/Övrigt

  • ISSN: 0003-0147