We use chemical biology to uncover biochemical mechanisms in innate immunity and, in parallel, develop therapeutic hypotheses and lead compounds. Innate immune pathways as the first line of defense against pathogens present many exciting opportunities for chemical biologists. These pathways are a rich source of novel chemistry: they involve diverse molecular patterns in pathogens, little-explored second messengers, and drugs with poorly understood mechanism. Activation of innate immunity is a proven therapeutic strategy for vaccination, viral infection, and cancer, while inhibition is a strategy for treating autoimmune diseases and sterile inflammation. To date, however, most modulators of innate immunity are broad, non-specific, and poorly characterized, such as killed bacteria, alum crystals, and steroids. The Li lab seeks to improve understanding of these pathways and facilitate the development of more precise drugs for preventing or treating specific diseases.