Major members of Unit 731 were given immunity for the information found in their experiments. I read a discussion by a few Redditors about how invaluable the information was both from the Japanese and the Germans, examples include how frostbite and air pressure affects the body.
However, I can't find any information on the significance of this data, it must have meant something for the US to grant immunity.
Edit: The recent string of my posts makes me seems a bit overly interested in the Axis powers, it's not what you think! I'm towards the end of my WW2 notes.
Hi, not discouraging other answers here, but while you're waiting, you can get started on this post featuring /u/commiespaceinvader
I can offer some context, what the people thought at the time/perceived valuable at the time. For example, the American intelligence agencies had some knowledge about what was going on in various Japanese research facilities, like Unit 731. They heard rumors during the war about the potential development of bio-warfare and supposedly they also had some written documents that supported these claims. They knew, for example, that the Japanese researched potential weapons like plague, cholera and typhus. So by that point American interest in these experiments started to grow. That was evident after the war, when Lt. Col. Murray Sanders was tasked with finding out what exactly the Japanese were researching and what were the results of said experimentation. Sanders proceeded to ask detailed questions like, how does one develop a bomb for bio warfare, how does one grow bacteria in a lab, how does one test potential weapons, ... USA was especially interested about the potential use of bio-warfare, even so, that they promised immunity to former members of the Unit 731 and Shiro Ishii himself came forward. American government wanted his cooperation so badly, they promised him, that all the data he would disclose, would remain top secret in order to prevent him being persecuted as a war criminal. One would have to believe that they contained something valuable, at least to the American government. There were also rumors that USA used said data and deployed some forms of bio-warfare (like plague) in the Korean war.
As for German experimentation, for example experiments on twins, curing of homosexuality and developing a truth serum all turned out to be rubbish. A lot of Nazi doctors pursued individual interests like such, which resulted in experiments that had zero scientific value. On the other hand, reversing hypothermia with hot bath proved to be the best treatment at the time and could be readily used in future. American Navy also claimed at the time, that the experiments involving pressure chambers could help save lives, as they helped improve their knowledge of physiology. There must have been something of interest or value, that the Americans recruited so much of German and Austrian scientists and doctors from 1945 forward. Again, this was the belief then.
Both groups shared some similar ideas about what they wanted to accomplish with experimentation, like preventing epidemics and developing cures (mainly that the army would not suffer losses), but if they really produced valuable scientific data is another question. As the German experimentation has already been described in detail by u/commiespaceinvader (https://www.reddit.com/r/AskHistorians/comments/4oyv9n/am_i_a_person_living_in_the_west_currently/ ) as already mentioned in this thread, I recommend you check out his comment. I can only add some general info about Japanese interests and goals with human experimentation. Like with Germans, we can also divide their experiments into three groups: prevention of epidemics in the army, gaining new knowledge that would further improve the army (like pressure chamber experiments in aviation) and development of potential biological warfare, that would be effective on the battlefield. They tested their ideas in labs, outside (on their compounds) and lastly on terrain, including on civilians. Some forms of experimentation, that were used on humans: prevention and later spreading diseases like ebola and plague, frostbite, hypothermia, vivisections, poisoning, exposure to mustard gas, drug overdose, pressure chambers. Example of one of the most rubbish experiments is the injection of horse urine into the kidneys of the victims, which had zero value.
I hope this answers at least some of your question.
Sources and further reading about various aspects of human experimentation during the WW2: