I've just spotted a new post, titled "The autoimmunity of Parkinson's disease?", on "The Science of Parkinson's disease" blog.
It is written in the usual folky SOPD style (with the usual number of typos and "gramos"), and contains a number of helpful diagrams.
The post is quite long, but I don't think it's necessary to read all of it, to get a lot out of it.
The autoimmunity of Parkinson’s disease? | The Science of Parkinson's disease