I use plant sterols/sterolins with my clients suffering from autoimmune conditions, such as rheumatoid or psoriatic arthritis, lupus, multiple sclerosis, scleroderma, psoriasis, eczema, autoimmune thyroiditis, etc.  Most commonly found in a patented product known as Moducare, the benefits surround balancing the TH1:TH2 response of the immune system.  This enables the immune system to fight bacterial and viral infections, while at the same time taming an overagressive immune response to the body's own tissues.  Moducare also helps with the hyperimmune response seen in allergic conditions.  See the top article to the left for a good overview of how Moducare works, and then explore the other articles as you are interested.  

Plant sterols and sterolins are also used to inhibit cholesterol absorption from food (I certainly do not use Moducare for that purpose, and if taken on an empty stomach it will not do this); another benefit is for the condition of benign prostatic hypertrophy (enlarged prostate).