Think of the poor dialysis patients in the days before EPO, who would have to receive blood transfusions all the time to keep functioning. It's a wonder that any transplants ever worked in them, given all the antigens they would build up from these repeated transfusions.
If you know you have surgery coming up and you are not in danger of severe anemia because of being on dialysis, you can avoid raising your antibody levels by having blood transfusions from another person by instead having your own blood extracted and stored prior to surgey. Then, if and when you need it during or after surgery, you can just have your own blood back with no risk of unscreened infections or of increasing antibodies.