Controlling cellular immune responses could help researchers to turn adult cells into embryonic-like stem cells without having to insert any genetic material.

The most efficient way to reprogram adult cells is to genetically alter them, but this can cause problems in cell therapy. John Cooke at Stanford University in California and his colleagues found that the viruses that are normally used to deliver reprogramming genes into cells alter the cells in another, unanticipated way. The inflammatory response to the virus induces changes that open up the structure of chromatin — the tightly packaged DNA and protein that makes up chromosomes.

Using virus-free reprogramming techniques and a synthetic molecule to activate an inflammatory pathway in adult cells, the researchers obtained 25 reprogrammed cell colonies per experiment. No such colonies were generated if the immune pathway was inhibited. Controlling inflammatory pathways could make it easier not only to produce genetically unaltered, reprogrammed stem cells, but also to direct cell fate in other ways.

Cell 151, 547–558 (2012)