A common problem that can occur during stem cell transplant procedures is that the recipient’s immune system may attack and thus reject the new cells by recognizing them as ‘foreign’. A solution may be on the horizon as scientists at the University of California San Francisco have recently managed to use the CRISPR gene editing tools to create stem cells that are effectively invisible to the body’s immune system. Because transplanted stem cells are viewed by the human body as foreign organisms and thus a potential threat, the immune system often kicks into high gear when the cells are detected. While there are some drugs that help suppress the immune system’s response, it also leaves the patient vulnerable to other diseases that can complicate matters. The modified stem cells created by the UCSF scientists present a potential solution to this problem by not setting off the immune system’s alarms in the first place. The breakthrough could eventually open up new possibilities for procedures that save, extend, and improve people’s lives.