One of the unfortunate side effects of bone marrow and stem cell transplantation is that the newly implanted cells often stage an internal attack against the patient they’re intended to help. Stanford University School of Medicine researchers now have a better grasp of this phenomenon, known as graft-versus-host disease, or GVHD, and have proposed a possible method of prevention: simple ultraviolet light. In a new animal study, researchers identified the principal culprit in GVHD: an immune cell in the skin known as a Langerhans cell. These cells normally function as flag posts for the immune system, signaling infection-fighting T-cells to come to a particular site to fight off a virus or bacteria. But in transplants, they do patients a great disservice, alerting T-cells to attack the patient’s own tissues, researchers found. The researchers were able to effectively eliminate the Langerhans cells in transplanted mice by exposing them to ultraviolet light, giving the animals mild sunburn. Transplanted mice that received this treatment experienced no GVHD while those that didn’t showed severe signs of the disease, said Edgar Engleman, MD, professor of pathology and medicine and senior author of the study.
