Is this the receptor antibody or an antibody to a variant of the ACH enzyme referred to as ACH-R? There is one scientist who believes ACH-R (an enzyme variant of acetylcholinesterase) is being produced in many with CFS/ME, effectively blocking the proper action of ACH which is to degrade acetylcholine. As we know the acetylcholine toxicity and or organophosphate poisoning symptoms are very similar to CFS.
I have read several studies on the subject and apparently in animals (under extreme prolonged stress) a gene turns on which causes ACH-R to replace ACH production (at least in significant amounts), making the ACH enzyme dysfunctional.
The evolutionary mechanism of this would supposedly be to tell the animal to "RELAX". This reasoning is my inference but the point in one research article on the subject was made that the ACH-R production gene was turned on in many cases for years after the stressor.
Serotonin antibodies have been found. I've never had the ACHr anti bodies tested..I am assuming you mean the receptor antibodies as are found in M.S.
In any event if the ACH-R enzyme turns on and acetylcholine builds to toxic levels constantly it would not surprise me if that could be a mechanism for the body to start destroying the receptors to lower the levels of acetylcholine.
This is highly theoretical. If I had to guess I would say hormones are still intimately involved in the regulation of the entire acetylcholine system.
