Collaborative Research: Constraints of biomass on innate immunity across terrestrial mammals

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This project addresses two long-standing questions in biology, how genomes become phenomes and how organisms maintain stability through change, by investigating how body size affects immune defenses in terrestrial mammals. Although body mass is one of the strongest influences on many physiological traits, effects of body size are not known for immune systems. Through an unprecedented comparative approach, the research tests whether body size explains why some species are more susceptible to parasites and more likely to act as parasite reservoirs, whereas other species are resistant. Specifically, the research will provide new information on how functional forms of innate immunity relate to body size among 150 zoo-housed terrestrial mammal species spanning a broad range of sizes. Results will provide a framework for understanding of mammalian immune variation has the potential to enhance models of disease spread by providing predictions about the level of immune defense expected in species never before studied. The project fosters career development for two young investigators, a postdoctoral researcher, and 8-10 undergraduate research students. Participants will develop outreach activities for zoos and for biology classes at local middle and high schools, to enhance the educational effectiveness of zoo exhibits and lesson plans. These activities will demonstrate how comparative research is relevant to understanding human and animal health.This project investigates whether and how body mass is related to the architecture of antimicrobial immune defenses in terrestrial mammals, an unstudied aspect of size-scaling. Host size likely affects i) the chance of exposure to infectious organisms, ii) the ability of immune defenses to keep pace with pathogen replication, iii) the ability of host surveillance mechanisms to detect threats in a comparatively large risk space. The project will determine how functional forms of innate immunity relate to body size among 150 zoo-housed species of terrestrial mammals spanning 7 orders of magnitude in body mass. In addition, protein expression for innate immune defenses as a function of body mass among 10 primate species spanning 5 orders of magnitude in size will be quantified. Using zoo-housed animals, which experience similar developmental histories in common environments, minimizes effects of confounding variables inherent to the study of wild individuals. Measuring functional antimicrobial responses is preferable to less direct assays of host defense. The transcriptomic methods will show which innate immune genes, gene networks, and/or gene modules are most sensitive to body mass. This project addresses two Grand Challenges in Organismal Biology, and has the potential to transform how scientists think about host-parasite interactions. The transcriptomic data generated will contribute to other systems biology pursuits, including understanding how size may constrain the evolution of regulatory processes in vertebrate animals. The participants, including 8-10 undergraduates, will develop interpretive displays and exhibits for zoos, and lesson plans for middle- and high-school biology classes to engage and educate students and the public and to demonstrate the relevance of comparative research.