Dynamics of PHA-induced immune response and plasma carotenoids in birds:should we have a closer look?

Abstract

SUMMARYAllocation trade-offs of limited resources are thought to ensure the honesty of sexual signals and are often studied using controlled immune challenges. One such trade-off between immunity and ornaments is that involving carotenoids. Phytohemagglutinin (PHA)-induced immune response is a widely used immune challenge, yet more details on the underlying physiological mechanisms and potential costs are needed. We investigated the temporal dynamics of PHA-induced immune response and associated changes in blood carotenoids, body mass and a carotenoid-based coloured signal. We found variation in individual response patterns to PHA after peak swelling was reached, with birds showing either a rapid or a slow subsequent decrease in swelling, suggesting variation in the duration of the immune response and/or inflammation. Body mass did not affect immune response. Plasma carotenoids followed a transient decrease closely matching the dynamics of the swelling. The peak of the immune response was negatively related to initial plasma carotenoid levels and positively correlated to the relative decrease in plasma carotenoids. Individual variation in duration of the swelling could be partly explained by plasma carotenoids; high initial carotenoid levels were associated with a slower decrease of the swelling. These contradictory effects of carotenoids suggest a complex role in the immune response. Bill colour was positively correlated to initial plasma carotenoid concentration but it did not predict or change as a consequence of immune response to PHA. Bill colour thus reflects medium-or long-term quality rather than immediate quality. Taking into account the dynamics of the immune response and that of associated physiological parameters would thus yield new insights into our interpretation of variation in PHA response.

Is oxidative status influenced by dietary carotenoid and physical activity after moult in the great tit (Parus major)?

“…Carotenoids are known to regulate and stimulate immune function (Hõrak et al, 2004;Biard et al, 2009;Cote et al, 2010;Hill and Johnson, 2012) and to participate in reducing oxidative stress (Surai and Speake, 1998;Blount et al, 2000;Isaksson, 2009). We experimentally investigated the influence of dietary carotenoids on oxidative stress in the great tit after moult, by simultaneously manipulating carotenoid availability and physical activity, the latter being an attempt to increase oxidative stress as a result of an increase in metabolism.…”

“…oxidative damage) in egg yolk (Surai and Speake, 1998;Blount et al, 2002) and in passerine adults and nestlings plasma carotenoid concentrations were positively correlated with plasma vitamin A and E concentrations (Biard et al, 2005(Biard et al, , 2007, which are important lipid-soluble antioxidants (Surai, 1999(Surai, , 2002. After an immune stimulation, plasma carotenoid concentration decreased in blackbirds Turdus merula (Biard et al, 2009) and in zebra finches Taeniopygia guttata (Alonso-Alvarez et al, 2004). Moreover, plasma carotenoid concentration was positively correlated with concentrations of lymphocytes and eosinophils in the great tit (Hõrak et al, 2004).…”

“…Vertebrates cannot produce these molecules, and must acquire them from food (Hill and McGraw, 2006;Isaksson, 2009). In addition to their role in pigmentation, carotenoids have multiple physiological roles Hill and McGraw, 2006) including regulating and stimulating immune function (Hõrak et al, 2004;Biard et al, 2009;Cote et al, 2010;Hill and Johnson, 2012) and participating in maintaining oxidative balance through their antioxidant properties (Surai and Speake, 1998;Blount et al, 2000;Isaksson, 2009).…”

Plasma carotenoid levels in passerines are related to infection by (some) parasites

“…A recent meta-analysis concluded that carotenoid levels in birds are related to individual immune response and antioxidant capacity (Simons et al, 2012). For example, the inflammatory/immune response elicited by the injection of a vegetal protein (PHA test) is associated to a decrease in the levels of carotenoids in blood (Biard et al, 2009). However, it is unclear if carotenoids act properly as antioxidants or just are affected by organisms antioxidant status (Simons et al, 2012).…”

Relação sazonal entre reprodução, energética e imunocompetência em sapos da Caatinga

“…The PHA injection stimulate an inflammatory response, the influx of lymphocytes, neutrophils, basophils, eosinophils and macrophages to the local of the injury (Martin et al 2003;Kennedy and Nager, 2006;Tella et al, 2008;Biard et al, 2009;Vinkler et al, 2010;.…”