For one of every three kidney failure patients, a transplant is not possible even if a potential donor's tissue and blood types otherwise match perfectly. This is because they have a highly sensitized immune system that would attack the transplanted kidney or pancreas.
If a person has become highly sensitized, his or her immune system is hyper-vigilant to invaders -- even when the invader is a life-saving transplanted organ.From Montefiore Medical Center
Q. What does "SENSITIZED" mean?
A. Approximately 30% of the 84,000 patients who are waiting for a deceased-donor kidney are considered "sensitized", and those with exceptionally high antibody levels are considered especially poor candidates for transplantation. People who have this type of antibody typically develop them through a previous exposure to foreign tissue, such as during pregnancy, prior transplant and blood transfusion. In fact, each year only 6.5% of highly sensitized patients receive a transplant. Sensitized patients wait 3-4 times longer than unsensitized patients for a compatible deceased-donor.