Its something no one would have anticipated or thought about,
Amazing that a doctor would make that statement. Guts of animals being sprayed in a person’s face is disturbing on many levels. How could it not be a problem?
How is a bone marrow recipient given marrow? It’s simply injected (into the bloodstream I presume), somehow it knows where to go.
Pig brains or a molecular component inhaled might get into the bloodstream somehow and attempt to cluster at nerve points.
The body ‘sees’ foreign invader and attacks.
Just a SWAG.