How the development of ideas and techniques since the 1800's has led to the present success of transplant surgery?

Because immuno suppressive drugs which suppress a natural immune response to an organism was not used in the early 1800s, the bodies kept on rejecting the foreign organs so the patient kept dying when the body sent antibodies to kill the transplanted organ, seeing it as a foreign body. Eventually immuno suppressive drugs were developed to stop the body rejecting and attacking the organ and so now there are very few rejections meaning there is a much higher success rate.