The present generation of therapies for rheumatoid arthritis are based on TNF inhibition - a fairly crude manipulation of the immune system when considered in the grand scheme of what is possible, but one that is getting better. From Technology Review: "A new protein engineered to inhibit molecules that cause inflammation not only reduces symptoms of rheumatoid arthritis in mice but also may have potential to reverse the disease's course. Researchers hope the findings will point toward a new therapy for this crippling and difficult-to-treat disease, which occurs when the immune system attacks the body's own joints. Even medications that are most successful in halting joint inflammation are effective in only about half of the patients who try them. ... The new synthetic protein [appears] to target TNF in a far more specific fashion and could be produced at a small fraction of the cost [of present TNF inhibitors]. ... a protein called progranulin binds to TNF receptors and that administering the protein to mice with rheumatoid arthritis reduced or even eliminated their symptoms. Then they determined which fragments of progranulin were responsible for binding to TNF and combined those fragments to engineer a protein that works even better to suppress disease. Mice with mild arthritis appeared to be disease-free after several weeks of regular injections of the modified progranulin."

Link: http://technologyreview.com/biomedicine/35091/