Insight into the way the thymus creates different types of T cell may allow us to manipulate immune responses therapeutically.

The thymus produces both 'effector' T cells that kill infected cells and 'regulatory' T cells that suppress unwanted immune responses. Both types of T cell arise from the same precursors, and a complex pattern of signalling between cells within the thymus dictates a developing T cell's final fate.

According to current thinking, a T cell is directed down the regulatory route if it binds to one of the body's own structures. Now, though, an international team led by Professor Adrian Hayday of King's College London School of Medicine at Guy's Hospital has found that a maturing cell can become a regulatory T cell without this binding step. The shift in fate was achieved by blocking a signal normally given to developing T cells by a pool of cells within the thymus.

This suggests a way to control whether T cells become effectors or regulatory – to boost an immune response (to attack cancer cells, for example) or to tame it (as in autoimmune disorders).

External links

• Pennington DJ et al. Early events in the thymus affect the balance of effector and regulatory T cells. Nature.