U.S. scientists have determined the human body's DNA, coupled with a peptide, ignites immune response usually aimed at fighting infections.

   The University of Texas M.D. Anderson Cancer Center-led research found a human peptide that acts as a natural antibiotic against invading microbes can bind with the body's DNA, triggering immune responses in the absence of an infection.

   "This combination of the peptide and self-DNA activates the same immune response pathway as a virus does," said senior author Dr. Michel Gilliet.

   Researchers said they believe that response is both a likely key driver of autoimmune disease and a system that flags tissue damage to launch a protective inflammatory response to injury.

   "We show that this pathway may drive autoimmunity in psoriasis, a chronic inflammatory skin disease," said Gilliet, who noted the key peptide -- called both LL37 and CAMP -- is also heavily expressed in other autoimmune diseases, such as inflammatory bowel disease and rheumatoid arthritis.

   LL37 provides a new potential target to block in the treatment of chronic inflammatory diseases and a possible component for vaccines against infectious diseases and cancers, the researchers said.

   The study is reported in the online edition of the journal Nature.

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