Reproductive State, but Not Testosterone, Reduces Immune Function in Male House Sparrows (Passer domesticus)

• Published in: Physiological and biochemical zoology 2005-01, Vol.78 (1), p.60-68
• Main Authors: Greenman, Chris G., Martin II, Lynn B., Hau, Michaela
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animal wings; Animals; Aviculture; Body Weights and Measures; Breeding seasons; Corticosterone - blood; Drug Implants; Immune system; Immunity, Cellular - drug effects; Immunosuppression; Male; Male animals; Molting; Molting - immunology; New Jersey; Photoperiod; Phytohemagglutinins - administration & dosage; Phytohemagglutinins - pharmacology; Radioimmunoassay; Reproduction - immunology; Seasons; Sparrows; Sparrows - immunology; Sparrows - physiology; Swelling; Testosterone; Testosterone - administration & dosage; Testosterone - blood; Testosterone - immunology; Time Factors
• ISSN: 1522-2152; 1537-5293
• DOI: 10.1086/425194

The immune system requires energetic and nutritional resources to optimally defend organisms against pathogens and parasites. Because resources are typically limited, immune function may require a trade‐off with other physiologically demanding activities. Here, we examined whether photoperiodically induced seasonal states (breeding, molting, or nonbreeding) affected the cutaneous immune response of captive male house sparrows (Passer domesticus). To assess immune function in these birds, we injected the mitogen phytohemagglutinin (PHA) into the patagium and measured the resulting wing web swelling. Molting and nonbreeding birds had similar immune responses to PHA injection. However, males in a breeding state showed lower immune responses than both molting and nonbreeding birds even though they did not actually breed. We tested whether this decrease in the PHA swelling response in birds in a breeding state was due to elevated plasma concentrations of testosterone (T) by administeringTto birds in a nonbreeding state. Contrary to some evidence in the literature,Tdid not suppress the response to PHA in house sparrows. Our data show that passerine birds show seasonal modulation in immune function, even in benign environmental conditions. However, even thoughTis often cited as a strong immunosuppressant, it is not fully responsible for this seasonal modulation.