Vaccinosis reactions occur in the same blood lines. However, it is equally clear that not all dogs within these groups will develop an autoimmune disease, the majority will live normal, healthy lives, although some may have sub-clinical autoimmune disorders. It seems likely that a dog must have a genetic tendency in order to develop an autoimmune disease. However, for overt disease to manifest itself specific insults to the animal's immune system must also be presented. The health of its immune system in general seems to be a major factor.
Dogs are at far more risk when they are already stressed by disease.
The reported incidence of autoimmune disease is on the rise, and there is some debate as to whether this is because it is really more common or because we are better at detecting it. I believe that both factors are probably involved. A couple of recent papers suggest that both an increase in pollution and an increase in sanitation could be problematic. Levels tend to be higher in rural areas where wells are the water source. Most commonly found are carbamate insecticides and triazine herbicides.