system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes ricin such a potent poison, and what makes it untreatable?
gpt
Ricin is a plant agent that gets into mammal cells and interferes with construction of some proteins.  Alas, your cells need those proteins to work correctly, and the ricin causes the cells it gets into to die.  Then it gets into the neighbor cells, etc.  Too many cells die, and you die.

There is no antidote.  Ricin has been known for a long time, and many folks have tried to find one.  Alas, none have been found.  The "treatments" mostly involve removing any ricin from the body that hasn't been absorbed and keeping the person alive as long as possible in hopes that the body's cleanup processes can clear the ricin out.  If too much has been absorbed into cells over too large a part of the body, then the person ultimately dies.