Type 1 diabetes may be caused by faulty versions of two genes that usually help the body to fight infection.

Joanna Howson at the Cambridge Institute for Medical Research, UK, and colleagues think that faulty variants of HLA-A and HLA-B lead the immune system to destroy insulin-producing islet cells in the pancreas. Usually, the two genes make components of MHC1 – a protein on the surface of immune cells that helps them tell friend from foe.

Sure enough, the team found that the class of immune cells known to attack islet cells were those activated by MHC1 (Nature, DOI: 10.1038/nature06406). …