Nels Elde investigates interactions between pathogenic microbes and their hosts. Specifically, Elde and his team compare host-microbe interfaces to understand how evolution acts to diversify immune systems and fundamental cellular processes. Combining evolutionary analysis and experimental approaches, the team pinpoints mutations and studies the impact of genetic variation. Their research is revealing new classes of antiviral genes and unexpected differences in core cellular and physiological processes. The team is also uncovering means by which viruses adapt to host defenses and the impacts of selfish genetic elements on the origins and regulation of immune functions. This work points to a central role for microbes in shaping cell biology.