NEW YORK, Oct 19 (Reuters) - For the first time, a pig kidney has been transplanted into a human without triggering immediate rejection by the recipient's immune system, a potentially major advance that could eventually help alleviate a dire shortage of human organs for transplant.

The kidney made "the amount of urine that you would expect" from a transplanted human kidney, he said, and there was no evidence of the vigorous, early rejection seen when unmodified pig kidneys are transplanted into non-human primates.

The recipient's abnormal creatinine level - an indicator of poor kidney function - returned to normal after the transplant, Montgomery said.

The NYU kidney transplant experiment should pave the way for trials in patients with end-stage kidney failure, possibly in the next year or two, said Montgomery, himself a heart transplant recipient.

The current experiment involved a single transplant, and the kidney was left in place for only three days, so any future trials are likely to uncover new barriers that will need to be overcome, Montgomery said.