When our immune system encounters a new virus—say, SARS-CoV-2—for the first time, some of our plasmablast B cells will release a first flush of antibodies that can stick to and even neutralize the virus. But those first antibodies are short-lived, typically don’t stick very strongly, and the cells that produce them don’t last longer than a few weeks.

For our comprehensive coverage and latest updates on COVID-19 click here.

As reinforcement, the immune system has a program in place to create long-lived plasma cells that secrete even better, more–tightly binding antibodies. This takes place in the germinal center, a transient, complex structure in the lymph nodes and spleen. There, different B cells gather and undergo a process that’s best described as evolution on the fast track. They rapidly proliferate while deliberately introducing random mutations to certain genes encoding antibodies, increasing the chances of producing a few clones that can squelch the virus.

A type of T cell picks and chooses progeny with promising antibodies, while killing the less useful ones or directing them back for improvement—a cycle of refinement and selection that culminates in the creation of long-lived, plasma B cells that can protect us against re-infection for years, and also memory B cells, which last for even longer. Without germinal centers, the body cannot make lasting antibody immunity to pathogens.