M.D. Anderson-led team reports possible key to autoimmu...( HOUSTON A human peptide that acts a...),Health

HOUSTON A human peptide that acts as a natural antibiotic against invading microbes can also bind to the bodys own DNA and trigger an immune response in the absence of an infection, a research team led by scientists at The University of Texas M. D. Anderson Cancer Center reports in an early online publication in Nature.

This combination of the peptide and self-DNA activates the same immune response pathway as a virus does, says senior author Michel Gilliet, M.D., assistant professor in M. D. Andersons Departments of Immunology and Melanoma Medical Oncology.

Researchers believe this response is both a likely key driver of autoimmune disease and an integral part of an early warning 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, Gilliet says. But 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 authors note.

The team tracked down this new pathway by studying the activation of important immune defense cells in psoriasis. Plasmacytoid dendritic cells (pDCs) are highly specialized to recognize viral and other microbial infections. They engulf a virus and set off an immune system cascade to fight the infection by producing interferons.

These dendritic cells normally do not respond to self-DNA, Gilliet explains. This unresponsiveness prevents the cells from launching an attack on the bodys own tissue. However, researchers had accumulated evidence of a connection betw
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