Control of autoimmunity by ‘epitope theft’

We all possess T cells with autoaggressive potential. Knowledge of their regulation is crucial for elucidating pathogenetic pathways and designing effective treatments for autoimmune diseases. A novel mechanism of T-cell silencing – in an autoimmune model – has recently been identified and is termed ‘epitope theft’. The ‘thieves’ are naïve CD8+ T cells, which apparently ‘steal’ MHC-class-I–antigen complexes from antigen-presenting cells (APCs). The deprived APCs can no longer activate other potentially pathogenic naïve CD8+ T cells that are specific for the same epitope. This phenomenon is a previously unrecognized antigen-specific mode of protection against autoimmunity.