So you know how you have dna? Well dna converts into amino acids and long chains of amino acids are called proteins. Proteins are the real workers in our body.

But you might think, if you knew the dna sequence, you know it all, correct? Not really. You see, dna is only 1 dimensional data. A lot of the information about the functions of a protein comes from its structure.

So really, if you have a correct dna converted into amino acid chain (a protein), it still needs to be in the correct shape or folding in order for it to function.

Prions are incorrect foldings of amino acid which obviously do not work. But whats more is that, when these folded structures come in contact with other functioning proteins, they can turn them into incorrect folding as well.

Since these proteins are still your own (ie they still came from your dna) the immune system doesn’t quite work on them like it would on a foreign substance like bacteria or virus.