I'm surprised the article didn't mention immune system mosaicism, where populations of immune cells have mutations that allow them to look for different protein

I'm surprised the article didn't mention immune system mosaicism, where populations of immune cells have mutations that allow them to look for different proteins. And I've heard a neuroscientist speculate that the reason there is so much brain mosaicism is to allow different neurons to express different surface proteins and allow them to recognize and avoid attaching to themselves.