Re: fusions of patients with auto-immune disorders ???
I think it depends on the auto-immune disorder. For example, if someone with systemic lupus were to contract AIDS, they would either die immediately or not be able to develop AIDS (just be a carrier possibly). I have systemic lupus and at 1-1/2 years post-op I'm finally fusing. I haven't rejected the hardware (it's stainless steel).
However, the lupus made my recover that much more difficult on a number of fronts and I have to be extremely careful about any kind of infection or bleeding.