Meeting Abstract

131.3  Tuesday, Jan. 7 14:00  Stress-immune interactions in a range-expanding bird: covariation in stress hormone and Toll-like receptor expression KILVITIS, H.J.*; LIEBL, A.L.; MARTIN, L.B.; Univ. of South Florida; Univ. of South Florida; Univ. of South Florida hkilviti@mail.usf.edu

The physiological traits that promote vertebrate range expansions are just beginning to be revealed. In Kenya, the site of a recent range expansion of one of the world’s most ubiquitous birds, the house sparrow (Passer domesticus ), regulation of glucocorticoids and the innate immune system appear integral to colonization success. In populations at the Kenyan range edge, birds release abundant corticosterone, the main avian stress steroid, when exposed to mild, short-term stressors; additionally, their circulating leukocytes also express high levels of Toll-like receptors (TLR) 2 and 4, molecules that enable the immune system to detect Gram-positive and negative bacteria, respectively. Although the immune and endocrine systems may have distinct functions to promote success in new areas, we asked whether positive covariation between these receptors might also manifest along the range expansion. Whereas some level of inflammation is protective, high TLR-2 and TLR-4 expression could lead to excessive pro-inflammatory cytokine production, escalating the risk of collateral damage. Such risks are particularly large in areas where novel parasites, which often cause damage via inflammatory exuberance, are most common. We therefore asked whether TLR expression in macrophage-dense tissues (i.e., livers and spleens) covaried with expression of glucocorticoid and mineralocorticoid receptor expression. Our goal was to discern whether the costs of inflammatory responses were offset in range-edge sparrows by high expression of receptors for immunosuppressive glucocorticoids. In older populations, we expected comparable co-expression but at lower magnitudes for both TLRs and GR/MR. Analyses are ongoing.