Ramnik Xavier, MD, is a leader in translating insights from human genetics and the microbiome into textured understandings of pathophysiology. He combines computational and integrative biology approaches with genetic, molecular, and chemical biology methods to identify immune mechanisms that are perturbed in disease. By examining the functions of genetic variants associated with complex immune-mediated diseases, he uncovers biological processes, including antibacterial defense and intestinal barrier function, that preserve tissue homeostasis and contribute to pathology. His longitudinal studies of the human microbiome in both health and disease characterize community structure and function, providing insights into how microbes continuously shape immunity. He pursues mechanisms by which the microbiome influences physiology by identifying metabolites that mediate interactions between the microbiome and organs such as the brain. Dr. Xavier furthermore identifies new biomarkers and targets for therapeutic intervention that hold promise for treating patients.