Meeting Abstract

S4.1-2  Sunday, Jan. 5 08:30  Just how much do antibodies cost? Nutrition and humoral immunity in wild Soay sheep GARNIER, R; WATT, KA; CHEUNG, C; PILKINGTON, JG; MCNEILLY, T; PEMBERTON, JM; NUSSEY, DH; GRAHAM, AL*; Princeton University; University of Edinburgh; Princeton University; University of Edinburgh; Moredun Research Institute; University of Edinburgh; University of Edinburgh; Princeton University algraham@princeton.edu

Nematode infection and malnutrition are hypothesized to generate a “Negative Spiral,” with synergistic detrimental effects on host immunity, health and fitness. A cornerstone of this hypothesis, and much of ecoimmunology, is that investment in immunity has nutritional costs. Obtaining evidence of such costs has proven challenging, however. The Soay sheep population of St. Kilda (Scotland) offers an opportunity to quantify costs, due to the availability of an extensive sample bank, a longitudinal dataset, and laboratory assays developed for veterinary research. Massive die-offs of these sheep (Ovis aries) occur in some winters, due to a combination of malnutrition and gastro-intestinal nematodes (notably Teladorsagia circumcincta). We previously detected that antibody-mediated immunity is positively associated with survival and negatively associated with reproduction in these sheep, but whether nutritional costs play a role is unknown. In the summer prior to three major die-offs, we thus assessed nutritional status of individual ewes by measuring several plasmatic markers: albumin, total proteins, blood urea nitrogen and creatinine. On the same set of individuals, we measured antibodies of various specificities and isotypes (including natural antibodies as well as antibodies specific to T. circumcincta and to self antigens). We first show how these markers of nutritional state and immunity are associated. We demonstrate that different antibody types incur differential nutritional costs, and that parasitism itself has detectable nutritional costs. We then discuss how these physiological costs relate to the survival of the sheep through the subsequent population crash as well as subsequent reproductive success.