Cell therapy is the area of medicine that uses cells to perform therapeutic procedures. These cells act directly at the site where there is a disease or structural or functional difficulty in the body. Cell therapy aims to treat the disease by restoring or changing certain sets of cells, or by using the actual cells to deliver treatment to the body. With cell therapy, cells are cultured or modified outside the body before being injected into the patient. The cells may be originally from the patient (autologous cells) or from a donor (allogeneic cells). Some therapies are considered cell and gene therapies. These therapies work by changing genes into specific types of cells and inserting them into the body.