The researchers showed that a molecular "brake pedal" called SOCS3 slows the biochemical activity of macrophages only if they have been stimulated by a particular cytokine, IL-6. Macrophages are immune system cells in the blood that are the body's first line of defense against infections. SOCS3 is one of the SOCS (suppression of cytokine signaling) family of molecules that act as brake pedals on biochemical signaling pathways that turn specific cell functions on or off.

The finding adds to the understanding of how a critical signaling pathway called JAK/STAT operates in macrophages and other immune system cells. The study also unexpectedly discovered why a lack of the gene for SOCS3 can lead to a potentially serious runaway inflammatory response in humans.

The two discoveries made by the St. Jude team help to clarify an important part of the complex activities of the immune system, according to Peter Murray, PhD, Infectious Diseases. "The more we know about how cytokines control immune system cells like macrophages, and how the JAK/STAT system works, the closer we get to being able to exert fine control on the immune response when medically necessary," he said. Murray is senior author of an article on the research, which appears in the June issue of Nature Immunology.

Anne-Laure Pauleau made the discovery as part of the St. Jude team. Pauleau was a member of the "Paris Seven Program," which brings researchers from France to work in St. Jude laboratories. Roland Lang, the paper's first author, modified the immune systems of mice to produce animals that had both normal macrophages as well as macrophages that lacked the gene for SOCS3. This allowed Pauleau to stud
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Contact: Bonnie Cameron
bonnie.cameron@stjude.org
901-495-4815
St. Jude Children's Research Hospital
29-May-2003