Tissue rejection
From Tardis Wiki, the free Doctor Who reference
Tissue rejection was a medical term that referred to the incompatibility of differing body tissue when transplanted. Mehendri Solon overcame this problem, an ability he later used when restoring Morbius. (DW: The Brain of Morbius)
Cyber-conversion only worked on Mondasians and humans. The genome of other species made the process falter, resulting in tissue rejection. (DWM: The Flood)
