Anyway to tell from where one's autoantibodies are produced?
"where the autoantibodies are produced"
... it's more a matter of "why" or "how".... and more about "autoreactivity" rather than "autoantibodies"
I guess the answer is infection. Rather, persistent infection. But the pathogen doesn't make the autoantibodies.
The persistent infection keeps the immune system evolving. Trying to attack the infection from more and more angles. Like diversification of the immune system's arsenal. This amplifies the autoimmune potential.
Basically, the infection leads to retarded B cells and/or T cells. So, lowered self-tolerance (recognizing who's a good guy and who's a bad guy), and increased immune response (hyperactive).
At that point, there's prob going to be autoantibodies, as there's just a bunch of autoreactivity. Subtle differences in each of us can result in an autoantibody to something antinuclear (ANA), or to a neurotransmitter receptor, etc. I think that's why all of us seem to display such a unique set of autoantibodies w/ a lot of diverse autoimmune conditions.
The likely cause of specific autoantibodies that end up forming from all this... well, a lot of it appears to be viral proteins that look very similar to our own proteins. Like, maybe they share extremely similar amino acid sequences.
And then there's an issue like TS-HDS antibodies, which a few of us have. It's basically a carbohydrate on a cell's surface, and a virus like Coxsackie can bind to and infect a cell w/ TS-HDS (Trisulfated heparin disaccharide IdoA-2S GlcN-S-6S). Our body recognizes this and the retarded immune cells are like "I'm gonna kill everything w/ IdoA-2S GlcN-S-6S".
Then you got destroyed peripheral nerve cells that have IdoA-2S GlcN-S-6S. Small Fiber Neuropathy
They talk about the potential B cell involvement in the autoimmunity in the article.
btw, these 2 "theoretical" types of autoimmunity are molecular mimicry and epitope spreading. This is a good article that covers some interesting stuff on the topic. Oldie but goodie -
https://pubmed.ncbi.nlm.nih.gov/11130456/