Phytohaemagglutinin injection assay and physiological stress in nestling house martins

SUMMARY Many animal ornaments may have evolved as signals advertising the quality of the bearer. The honesty of the information content of these signals would rely on the costs associated with their expression, these being relatively greater for low-quality than for high-quality individuals. Given the physiological functions of carotenoids, carotenoid-based ornaments could indicate individual immunocompetence, and possibly the ability to mount an immune response at a lower cost. We evaluated whether the red carotenoid-based coloration of male red-legged partridges (Alectoris rufa) predicts the capacity of the individual to counteract the oxidative stress generated by a cell-mediated immune response. Individuals were subcutaneously injected with phytohaemagglutinin (PHA) or phosphate buffer solution (PBS) as a control. We found that eye ring pigmentation predicted the change in the amount of peroxidized lipids (TBARS) in blood after the PHA-induced inflammatory challenge. The degree of pigmentation of this carotenoid-based ornament was also negatively related to individual changes in γ-glutamyl transferase (GGT), another biomarker of oxidative stress involved in antioxidant metabolism (i.e. glutathione recycling). However, changes in circulating carotenoids did not significantly explain changes in lipid peroxidation or GGT levels, suggesting that the higher resistance to oxidative stress of those individuals with more pigmented eye rings was not directly mediated by their greater circulating levels of carotenoids. Our results indicate that carotenoid-based coloration can predict not only immune responsiveness (more coloured males mount greater responses) but also an individual's ability to counter the oxidative stress generated during immune challenge (more coloured males experience less oxidative damage when mounting an immune response).

Section: General Proceduresmentioning

confidence: 99%

Carotenoid-based coloration predicts resistance to oxidative damage during immune challenge

Pérez‐Rodríguez

Mougeot

Alonso‐Álvarez

2010

“…Although PHA-induced skin swelling is not a cost-free reaction (e.g. Alonso-Alvarez and Tella, 2001), it seems to elicit a more local response (compared with LPS or SRBC intraperitoneal injection) with few relevant systemic effects (Merino et al, 1999;Hõrak et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Cell-mediated immune activation rapidly decreases plasma carotenoids but does not affect oxidative stress in red-legged partridges (Alectoris rufa)

Pérez‐Rodríguez

Mougeot

Alonso‐Álvarez

et al. 2008

SUMMARYIn animals yellow-orange-red sexual traits pigmented by carotenoids have been suggested to act as signals of current health. Because carotenoids have important physiological functions, individuals might trade-off allocating these pigments to selfmaintenance versus coloration. Carotenoids may act as scavengers of free radicals that are released during an immune response. Here, we experimentally assessed whether a local cell-mediated immune response affects circulating carotenoids, antioxidant status, oxidative damage and the expression of a carotenoid-based trait. Male red-legged partridges (Alectoris rufa) were subcutaneously injected with phytohaemagglutinin (PHA) or with phosphate buffer solution (controls). The effect of the treatment on circulating carotenoids, total plasma antioxidant status (TAS), lipid oxidative damage in erythrocytes (TBARS) and ornamentation was assessed. Immune challenge induced a 13% decrease in circulating carotenoids within 24·h. However, this treatment did not affect TAS, TBARS or coloration. Coloration, circulating carotenoids and cell-mediated immune response were positively correlated, but these were not related to TAS or TBARS. Carotenoids were only weakly related to TAS after controlling for the effect of uric acid levels. These results suggest that carotenoid-based ornaments may honestly indicate immunocompetence but probably not antioxidant capacity in this species, and that carotenoids might be relatively weak antioxidants in the plasma. Furthermore, even a relatively harmless and locally elicited immune challenge had important effects on circulating carotenoids, but this effect did not appear to be associated with oxidative stress. Alternative mechanisms linking carotenoids to immunity (not necessarily relying on the use of these pigments as antioxidants) should be considered in future studies on birds.

“…Saino et al, 1997;Saino et al, 2001;Christe et al, 1998;Merino et al, 1999;Merino et al, 2000;Szép and Møller, 1999;Szép and Møller, 2000). They frequently face periods of food shortage incurred by unfavourable weather conditions (Bryant, 1975;McCarty and Winkler, 1999;Lifjeld et al, 2002), which adversely affect their immune function (Christe et al, 2001;Lifjeld et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Relationship between avian growth rate and immune response depends on food availability

Brzęk

Konarzewski

2007

SUMMARY Life history theory predicts that when resources are limited growing organisms are likely to trade an immune response for competing demands of growth. To test this we examined the effect of energy intake on body mass increments and an immune response in hand-reared sand martin (Riparia riparia) nestlings. We subjected the nestlings to three different feeding regimes, mimicking the range of food availability in the wild, and then evaluated nestlings' immune response to phytohaemagglutinin (PHA). Direction of correlation between the magnitude of PHA-induced swelling response and body mass increments depended on food availability: it was negative when food was scarce and positive when resources were plentiful. There was no significant correlation between the two traits under intermediate feeding conditions. We conclude that the relative cost of immune function in young birds depends on food availability and, therefore, may be modified by external factors such as weather conditions or hatching asynchrony.