I don't really know why, as I know nothing about this area, but I feel instinctively sceptical when I hear people talk about immune abnormalities in CFS.
I defy anyone to actually read through that history of scientific results going all the way back to 1983, and still doubt that there is ample evidence of immune abnormalities in ME/CFS. It might be best to start with the most recent research, going backwards from page 95. Yes, a 63-page summary of 30 years of scientific evidence of immune abnormalities in ME is a bit much to wade through. I'm not suggesting you read every word, but as you scan through it you should see that, although there are complexities and contradictions as the science evolves historically, there's also a fairly clear and evolving picture of the science as well, with multiple researchers over decades refining the same findings: impaired natural killer cell function, abnormal levels of lymphocytes, particularly during and after exercise, and multiple lines of evidence for chronic immune activation.
There is just too much of this evidence, from too many respected researchers, for it to be dismissed. Indeed, that's why the MRC recently acknowledged this evidence in their call for research. If you're sceptical about Margaret Williams, what do you think about this statement, from the MRC?
Immune dysregulation: There is evidence for a disturbance in innate and adaptive immunity in CFS/ME including alterations in cytokine profile, absolute and functional alterations in T cells and NK cells and occurrence of autoantibodies and allergic reactions that may explain some of the manifestations such as fatigue and flu-like symptoms. A number of infectious and environmental exposures have been associated as triggering these changes.