Yes, I agree. With autoimmune (IBD, stomatitis, pemphigus, etc.), the immune system sees the body or certain organs as "foreign" and mistakenly attacks it. This continued action without management destroys healthy tissue. Steroids come into play to say, "hey, slow down, leave the body alone."
With autoimmune disorders, the immune system is in overdrive and is attacking the body. The steroid ratches down the immune response. http://www.nlm.nih.gov/medlineplus/autoimmunediseases.html
The big one with kitties is IBD where the immune system is attacking the digestive tract. That's why so many kitties with IBD are on steroids.
With immune-compromised kitties (FIV, FeLV, cancer, etc.), immuno-stimulants are commonly used.
You typically do not want to use immuno-stimulants for autoimmune disorders. There are supplements and holistic treatments that fall into a sort of immune-modulator category that neither stimulant or suppress the immune system that could provide overall system support.