The immune system relies on B cells and their ability to make antibodies against an extremely broad range of pathogens. This broad responsiveness bears some risk, as B cells can also turn against healthy tissue – a phenomenon called autoimmunity. Scientists from the lab of Meinrad Busslinger now reported in the journal “Nature Immunology” how the protein lkaros orchestrates the fine balance between B cell silencing and activation – and thereby controls autoimmunity.