I disagree, science knows very little about how our immune system develops. They are just finding out our immune system is made through interactions with our environment. That gut bacteria are a large part of our immune system and play a huge role in our psychological health. Science also just discovered epigenetics a second code of DNA that codes everything we interact with in our environment and passes this data on to the next generation.

http://onlinelibrary.wiley.com/doi/10.1111/gbb.12109/full