Our bodies can fine-tune the immune response to an infection and make it proportional to the threat at hand. New research from Karolinska Institutet in Sweden describes how B lymphocytes, the immune cells that make antibodies, choose between different cell fates to balance the magnitude of the acute immune response and the memory response that protects against future threats. The study, published in Immunity, may contribute to the optimisation of vaccines to fight viruses or other pathogens.