Researchers have moved a big step closer to halting the progress of autoimmune diseases such as rheumatoid arthritis and diabetes by cloning the protein "receptor" that helps trigger them in the first place.

Immunex Corp. of Seattle announced Friday its success in cloning the Interleukin-1 receptor. Excess production of Interleukin-1 has been linked to various autoimmune diseases.The details of the discovery are contained in an article in the latest issue of Science magazine.

Dr. Steven Gillis, executive vice president of Immunex, said the protein receptor acts like a lock, into which the Interleukin-1 cell fits like a key to activate certain body functions, such as the growth of skin cells and the production of various types of white blood cells.

But when the inflammatory response is prolonged through excess Interleukin-1 production, it can cause excessive pain and discomfort and eventually lead to bone and cartilage deterioration, as well as other significant health problems.