CAMBRIDGE, Mass. (AP) _ Scientist today reported preliminary evidence that the natural hormone interferon can relieve the pain and swelling of rheumatoid arthritis.

The research, which will be reported in the journal Biotechnology, was conducted by scientists of the genetic engineering firm Biogen. Two experiments in Germany and the United States suggest that interferon can relieve symptoms of arthritis in people who are not helped by standard drugs.

Interferon is a natural protein produced by many cells in the body to fight disease. In the latest work, doctors gave patients a variety called gamma interferon, which is produced naturally by white blood cells called T cells.

The hormone was once in short supply, but it is now produced in large quantities by gene-splicing techniques.

The studies indicate that about two-thirds of the arthritis patients who take interferon seem to be helped. But experts are unsure whether it affects the underlying disease or simply eases symptoms.

Rheumatoid arthritis is an inflammatory joint disease, and it's thought to result from a misguided attack by the body's disease-fighting immune system. Experts estimate that it affects about 6 million Americans, and 10 to 20 percent of them are not helped by traditional therapy, such as anti- inflammatory drugs, gold salts and penicillamine.

Dr. Seth Rudnick, vice president for pharmaceutical development at Biogen, said it's too soon to know whether interferon will prove to be safe and effective in the treatment of this disease.

Doctors first noticed interferon's apparent effect when treating cancer patients who also had arthritis.