Autoimmune diseases are caused by the failure of an organism to recognize its own constituent parts, resulting in an immune response against its own cells and tissues. Against such diseases doctors use drugs based on gold, but until now nobody knew why they work. Moreover, such gold drugs have all sorts of side effects and take months before improvements are seen but unless scientists know the exact cause behind the beneficial effects it's difficult for them to know what exactly should be changed.

The gold treatment for autoimmune diseases, such as Systemic Lupus Erythematosus, Sjögren's syndrome and Rheumatoid Arthritis, was discovered by a French doctor, Jacques Forestier, in the 1930s. It is interesting to note that he discovered the treatment due the erroneous belief that rheumatoid arthritis was related to tuberculosis. In 1890 the German doctor Robert Koch had found that TB bacteria were killed by gold. So, Forestier also tried the remedy on rheumatoid arthritis - and it worked. For a totally different reason.

Brian DeDecker and Stephen De Wall from the Harvard Medical School's Department of Cell Biology were looking to develop a better drug for autoimmune diseases when they found why gold functions.

"We were searching for a new drug to treat autoimmune diseases," says DeDecker. "But instead we discovered a biochemical mechanism that may help explain how an old drug works."

They have found that special forms of gold, platinum, and other classes of metals work against the immune system by detaching bacteria and virus particles from a key immune system protein, the MHC class II proteins.

The immune system functions in the following way: The organism produces substances (called antibodies) which are specific to a certain pathogen (such as a bacterium or virus). The antibodies are produced by certain cells called the B cells, and are stuck on the surface of these cells. The antibody binds to the pathogen. When a certain pathogen enters the organism, the B cells having that specific antibody, multiply. This is the immune response to a certain infection.

The organism fights a new disease by producing large numbers of slightly different B cells, i.e. the existing B cells mutate in various ways, until some of these mutated B cells finally have antibodies capable of successfully binding to the new pathogen. At this moment this particular, successful B cell multiplies. In this way, the organism is capable to adapt to the appearance of new disease, and to keep pace with the evolution of microbes and viruses.

The other part of the immune system is made of T cells (there are several types of such cells each working in a somewhat different manner). These cells basically destroy the B cells that have attached to a pathogen, thus eliminating the pathogen.

In case of autoimmune diseases the B cells "think" that other genuine cells are in fact intruders. Usually this does not happen because each cell has a certain "tag" that identifies it as a proper worker. The MHC proteins are involved in this process of tagging the cells.

However, the gold drugs against autoimmune diseases don't address the cause of the disease. Scientists have now found that they simply work by detaching the cells from the grip of the B cells.

The researchers haven't started by studying the gold drugs; they were studying other drugs and identified that one of them, Cisplatin, worked because it contained Platinum. From here they made the connection with the gold drugs and made further experiments with gold.

Due to the fact that scientists now know the exact mechanism of gold drug action further drugs can be tested and explored in the lab, directly on diseased tissues. This may lead to a new generation of gold-based drugs for treating rheumatoid arthritis and other autoimmune diseases that are more effective and have fewer side effects.