Graft versus Host Disease (GvHD) is a complication arising in patients receiving stem cell transplants characterized by the donor-derived immune cells attacking the recipient's tissue. A variety of mouse models exist to study the development and treatment of this disease in a pre-clinical setting. Allograft models, also called mismatched, consist of donor cells from a different strain of mice than the recipient. Xenograft models are generated when donor cells are obtained from a different species than the host, such as when human cells are implanted into a mouse.