A type of cell that normally prevents a harmful autoinflammatory disease can, under certain inflammatory conditions, cause the disease in a mouse model.

A team led by Jeffrey Bluestone of the University of California, San Francisco, studied regulatory T (Treg) cells in a mouse model of an autoimmune disease in which the body attacks its own nerve tissue.

Treg cells expressing the Foxp3 gene normally act to suppress these harmful immune attacks. However, during the inflammatory response, a subset of the Treg cells expressed lower levels of Foxp3 and higher levels of proteins called cytokines.

These unstable Treg cells were predominantly present in the antigen-specific Treg compartment and induced anti-self immune reactions when transplanted into other mice. However, treating the Treg cells with the anti-inflammatory cytokine interleukin 2 restored the cells' protective abilities.

Immunity 39, 949–962 (2013)