"Th17 cells draw in other immune cells to the site," Murphy says. "It makes the Th17 cell a bit like the instigator of an autoimmune riot-lots of cells rush in, and harmful things can start to happen."

Batf is a transcription factor, which means that the protein made from the gene acts to turn the production of proteins from other genes on and off. Its only previously identified role was as a partner with another common transcription factor.

Schraml showed that Batf had to be present for Th17 cells to make ROR-gamma-T, the only other gene known to force T cells to become Th17 cells. She also found that the presence of Batf made it possible for T cells to make more IL17.

"Normally transcription factors do not make ideal drug targets, but our Batf-knockout mice provide a unique tool to find the other proteins that are important in the development of Th17 cells," says Murphy. "Those proteins could be good targets for treatments for autoimmune diseases."

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