So, I was in Biology Class about 30 minutes ago and during the Lecture my Professor mentioned Antigens. I remembered that antigens had something to do with the type of blood people have. Basically, due to my minor in Cyber Security and my newfound personal obsession with encryption and keys and how they work, I was thinking (well first off, I was thinking that the body doesn't cryptographically sign cells, but how cool it would be if it did) what would be the effects of signing cells, not only on the body, but also the history of the human race. Could the human race have somehow become more immune to certain/all diseases such as AIDS because of this? For clarification, if needed I can specify where the components of this cryptographic system would be stored in/out of the body. There is a public/private keypair.
Basically, the World Building part of this question comes from how would the history of the human race be effected by these differences in the body.
Edit 1: To clarify the idea I was thinking of, I was thinking that if cells could be cryptographically signed (not encrypted), then when other cells see it, it could verify the authenticity of the cell and choose whether or not to destroy it based off of the signature. (e.g. White blood cells destroying rogue blood cells because they don't match the signature of the person that it's living in) (The cells are allowed to mutate upon reproduction, they just have to be verified by others (before resigning) to be "clean", in other words, not harmful to the person). The idea is that the body can sign all its cells like files on a computer and verify that nothing unauthorized changed it in order to prevent diseases that can permanently modify human DNA will be destroyed and not hide from the body by pretending to be a valid cell.