Developmental corticosterone treatment does not program immune responses in zebra finches (Taeniopygia guttata)

Abstract

Developmental conditions may impact the expression of immune traits throughout an individual’s life. Early-life challenges may lead to immunological constraints that are mediated by endocrine-immune interactions. In particular, individual differences in the ability to mount immune responses may be programmed by exposure to stressors or glucocorticoid hormones during development. To test this hypothesis, we experimentally elevated levels of the glucocorticoid hormone corticosterone during the nestling and fledgling periods in captive zebra finches (Taeniopygia guttata). We subsequently challenged birds with the antigen lipopolysaccharide (LPS) on days 60 and 100 post-hatch to determine if developmental exposure to elevated corticosterone impacted the later response to LPS. As measures of immune function, we quantified bacteria killing ability, haptoglobin concentrations, and LPS-specific antibody responses at multiple time points. We also measured circulating corticosterone concentrations during the experimental period and on day 60 before and after endotoxin challenge. During the experimental period, corticosterone treatment elevated corticosterone levels. Corticosterone treatment did not induce programming effects on immune function or corticosterone production. Independent of treatment, individuals with higher corticosterone concentrations during the nestling period had lower bacteria killing ability on day 36 and higher baseline corticosterone concentrations on day 60 post-hatch. These results suggest a limited role for corticosterone exposure during early life to mediate immunological constraints later in life. Manipulation of cortisol may be necessary to conclusively determine if developmental glucocorticoid exposure can program immune function in birds. To determine if developmental stress can program the immune response, exposure to environmentally relevant stressors should also be manipulated.

Population history with invasive predators predicts innate immune function response to early life glucocorticoid exposure

“…Michaut et al, 1981;Avitsur et al, 2006;Schmidt et al, 2015). To verify whether early-life stress can program the immune response, direct manipulation of glucocorticoids and environmentally relevant stressors in early life is necessary (Grindstaff and Merrill, 2017). The immune-suppressive effects of exposure to stressors during early life (henceforth 'early-life stress') have primarily been studied in humans (e.g.…”

“…Michaut et al, 1981;Avitsur et al, 2006) and birds (e.g. De Coster et al, 2011;Kriengwatana et al, 2013;Schmidt et al, 2015;Grindstaff and Merrill, 2017), with less known about lasting effects of early-life stress on immune function in ectotherms. Ectotherms are unable to internally regulate temperature and may allocate resources toward the immune system in a different manner from ectotherms (Zimmerman et al, 2010); thus, ectotherms may experience different immune consequences of early-life stress compared to endotherms.…”

Introduction to ecoimmunology: An integrative approach

“…Specialized approaches are also available in a number of species, including assessing acquired immunoglobulin Y titers in birds (Kelly et al, 2017). Specific antibody responses to lipopolysaccharide (LPS), a mitogen used to mimic bacterial infection, were assessed in zebra finches (Grindstaff & Merrill, 2017).…”

“…Invertebrate species investigated in this current issue are the bumblebee ( Bombus impatiens ), the weevil ( Curculio sp., Coleoptera), the gallfly ( Eurosta solidaginis , Diptera), and larvae of the lepidopteran Pyrrharctia isabella (Czerwinski & Sadd, ; Ferguson & Sinclair, ). Avian species include the house wren ( Troglodytes aedon ), the golden eagle ( Aquila chrysaetos ), the song sparrow ( Melospiza melodia ), the European starling ( Sturnus vulgaris ), and the zebra finch ( Taeniopygia guttata ) (Bowers, Sakaluk, & Thompson, ; Grindstaff & Merrill, ; Kelly et al., ; MacColl et al., ; Pryor & Casto, ). Reptilian species represented in the current issue are the green anole ( Anolis carolinensis ), the gopher tortoise ( Gopherus polyphemus ), and the snapping turtle ( Chelydra serpentina ) (Beck, Thompson, & Hopkins, ; Goessling et al., ; Tylan & Langkilde, ).…”

“…Their study showed that exposures to the neonicotinoid pesticide, imidacloprid, altered immunity, and that exposure to the pesticide followed by an immune challenge significantly decreased survival, suggesting critical health consequences for pollinators facing multiple stressors (Czerwinski & Sadd, ). However, early life exposure to elevated corticosterone did not affect the immune response of zebra finches as assessed by an LPS challenge or by bactericidal capacity (Grindstaff & Merrill, ).…”