Dr. Hartigan-O'Connor's research focuses on development of the human immune system and interaction of that system with agents of chronic infection such as the human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Most recently he has studied development of Th17 cells, regulatory T cells (T-regs), and antigen-presenting cells in the mucosal immune system. He is interested in the relationship between variable development of such immune cells and variable control over chronic infectious diseases. He is also fascinated by the interactions between the normal gut microflora, pathogenic organisms, and immune cells within the intestine.