B Cell Programming in Early Life Found to Influence Long-Term Immune Health

B cells are part of our bodies' complex first line of defense against foreign microbes, with memory B cells playing an essential role in remembering past antigens. New research from Lund University, recently published in Immunity, suggests that the origin and development of these B cells impact long-term immune health, particularly within the gut.

"We found that a substantial portion of adult B cells develop in the first days of life after birth. We hope the resolution of this time window of when B cells come to be will cause others in the field to reevaluate and interpret their results in a new way," says senior author Joan Yuan, Associate Professor at Lund University.

While a longstanding immune system theory suggests development occurs in layers, with different cells arising at different times throughout development, the team found that the most significant wave of B cell development occurs during early life. Researchers utilized genetic techniques to label immune cells in mouse models to learn more about how many B cells are generated during different life stages, with some novel discoveries in the gut.

"Together with researchers from the immunology section at Lund University, we found that many B cells in the gut are also made during this early window of postnatal life and maintained in the adult. They exist in a mutually symbiotic way with microbes, where the B cells react to our gut bacteria, and the presence of the bacteria also promotes the maintenance of these cells," says first author Stefano Vergani, a postdoctoral researcher at Lund University.

The gut is the primary source of antibody production in the human body and is home to many B cells. As opposed to those found in the spleen or lymph nodes, this group of B cells is still relatively perplexing since it's unclear when they originate. Investigators used a mouse model of rotavirus infection to better understand how these early-life B cells function and discovered that infection during infancy caused gut B cells to develop different antibodies than exposure during adolescence.

"Given the similarities in mammalian development our findings suggest that as adults, a significant portion of our B cells, both in the gut and elsewhere, are formed very early on in life. Where the first few days after birth could potentially be a time where our immune responses are programmed for the long-term. This means that early exposure to an antigen could possibly dictate the trajectory of our immune health and our susceptibility to disease and allergies later in life," states Yuan.

These findings suggest that the cells developing in early life may impact the overall immune system down the line, as well as open several new avenues for investigating how microbial exposure and various illnesses affect long-term immune health.