Dr. Hanash is a physician-scientist studying the immunology of hematopoietic transplantation. His laboratory uses a combination of in vivoexperimentation, ex vivo modeling, and microscopic imaging studies to connect molecular expression to in vivolocalization and investigate pathologic and protective immunity occurring after bone marrow transplantation (BMT). Gastrointestinal (GI) injury is a frequent complication of clinical hematopoietic transplantation, and a major emphasis of their research is studying how the immune system influences the intestines and intestinal stem cells (ISCs). Their work has demonstrated that the ISC compartment is the initial region of the GI tract targeted by donor T cells after allogeneic BMT, that these T cells can directly kill ISCs upon their arrival, and that administration of Interleukin-22 may augment the recovery of the intestinal epithelium post-transplant.