Should gratitude be a requirement for access to live organ donation?

Gratitude is both expected and problematic in live organ donation. Are there grounds to require it, and to forbid access to live donor transplantation to a recipient who fails to signal that he feels any form of gratitude? Recipient gratitude is not currently required for organ donation, but it is expected and may be a moral requirement. Despite this, we argue that making it a condition for live organ transplantation would be unjustified.