White Rat, Black Leg (1) (IMAGE) University of Pittsburgh Caption This white rat received a donor leg from a black rat - a complete mismatch - and yet his body has been trained to accept the new limb as if it came from his twin. Best of all, his immune system remains intact. Credit UPMC Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.