Various people suffereing from various autoimmune diseases (Crohn's, MS, AIDS, etc.) have been doing personal experiments with Low Dose Naltrexone. The above cited paper gives support to the idea of natural opiates modulating immune response in the body. There is very little money to be made from this research, if successful, so drug companies have no interest.
However, if you suffer from an autoimmune disease - you may want to investigate further.