The early years are critical in terms of setting our bodies up for a lifetime of health
Early life is a critical time when the immune system learns to recognize gut bacteria and sets up surveillance that keeps them in check, researchers have found.
Defects in these mechanisms could help explain why the immune system sometimes attacks good bacteria in the wrong place, causing the chronic inflammation that’s responsible for inflammatory bowel disease, the study’s authors note.
“From the time we are born, our immune system is set up so that it can learn as much as it can to distinguish the good from the bad,” study author Associate Professor Matthew Bettini said.
“Our studies make clear that there is a window in which gut microbiota have access to the immune education process. This opens up possibilities for designing therapeutics that can influence the trajectory of the immune system during this early time point.”
The findings are significant not only for the influence they may have on nutrition, health and safety programs offered in early childhood education and care settings, but also for deepening an understanding of the holistic role of gut health in overall wellbeing throughout life.
In reaching their findings, researchers discovered ways in which the resident gut microbiota shape the developing immune system, finding that specialized immune cells capture pieces of bacteria and carry them over long distances, from the gut to the thymus.
Located in the chest, above the heart, the thymus is a gland responsible for “educating” immune T cells. Delivery of the cargo prompts the thymus to produce T cells that are targeted to the microbiota. Then, the T cells exit the thymus to surveil lymph nodes, the gut, and other sites in order to keep the bacteria under control.
“Our study challenges previous assumptions that potential pathogens have no influence on immune cells that are developing in the thymus,” Associate Professor Bettini explained.
“Instead, we see that there is a window of opportunity for the thymus to learn from these bacteria. Even though these events that shape which T cells are present happen early in life, they can have a greater impact later in life.”
T cells programmed to target beneficial bacteria could double as defense against closely related “bad” bacteria. During the study, which used mice to track the movement of cells around the body, mice populated with E.coli at a young age were more than six times as likely to survive a lethal dose of Salmonella later in life.
The results suggest that building immunity to microbiota also builds protection against harmful bacteria the body has yet to encounter.
“From the time we are born, our immune system is set up so that it can learn as much as it can to distinguish the good from the bad,” researchers said.
“Delving into these early communications between the body and microbiota demonstrates just how important it is to prime the immune system right from the start.”