If you hold your ACL replaced by a cadaver do you inevitability to rob anti-rejection drugs? If not, why not?

Obviously if you have a kidney transplant you have need of to take anti-rejection drugs. I've hear of plenty of athletes having cadaver ACLs implanted but never hear of them having to pilfer anti-rejection drugs, do they? And if they don't, why not? Ligaments are collagen fibers, there do not hold living cells contained by them, and as such cannot be recognized as foreign by the immune system.