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When the body’s B cell training grounds stay open after hours

If B cells are the munitions factories of the immune system, manufacturing antibodies to neutralize harmful pathogens, then the tiny biological structures known as germinal centers are its weapons-development facilities. Formed in response to infection and vaccination, these microscopic training grounds allow B cells to perfect the antibodies they deploy against specific viruses and bacteria.

Figuring out how germinal centers work is therefore crucial to understanding immunity and developing more effective vaccines. Now, a new study in Cell reveals why some germinal centers persist for months rather than weeks, providing insights that could inform future vaccine design.

Old bottle, new wine

Germinal centers form in the body’s lymphatic tissues shortly after vaccination or infection. Once inside a germinal center, B cells undergo rapid mutations and, through a process of natural selection, only B cells with antibodies that most effectively bind to their target antigens survive. These superior B cells then become either plasma cells, antibody factories that secrete copious amounts of antibodies into serum, or memory B cells, which patrol the body for signs of return of the pathogen they evolved to fight.

“The goal of the germinal center is to generate high-affinity plasma cells and memory B cells, that it then exports” says Renan V.H. de Carvalho, a postdoctoral fellow in the laboratory of Gabriel D. Victora at The Rockefeller University.

In mice, most germinal centers shut down after a few weeks, having accomplished their goal of producing high-affinity B cells. But those that form in response to certain respiratory infections, including the flu, can stay in business for more than six months, roughly a quarter of a mouse’s normal lifespan. De Carvalho and his colleagues wanted to understand why these germinal centers are so long-lived, and what precisely goes on inside them.

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