Allogenic transplants are cells collected from relatives of the patient. The transplant requires additional high intensity chemotherapy and radiation in order to destroy cancerous cells. In the process, many normal bone marrow cells are also destroyed. This is the reason for transplanting stem cells. The stem cells help to build new functioning bone marrow, red cells, white cells, and platelets. In addition, the immune cells from the donor are implanted into the recipient s body and help to fight off infection and kill remaining cancerous cells.