adaptation to the world. A new study suggests newborns suppress their immune system to stay healthy while bacteria colonize their gut.
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One of the biggest vulnerabilities of infants is largely invisible: In the weeks following birth, babies are particularly susceptible to infection because their immune systems are not fully functional. There are a handful of theories to explain this responsibility, and now a research team added another to the list: immune suppression in early life may help prevent inflammation in the intestines of infants they become colonized by helpful bacteria they need to stay healthy.
Newborns are more likely than older babies to catch, and die, severe infections. The reason is fuzzy indeed, there may be more than one explanation. One theory is that as the brain, lungs, and the rest of their body, the immune system of infants have simply not yet fully matured. Another is that mothers are to their in utero and two companions suppressed the immune system, so that neither rejects the other. After birth, the thinking goes, it takes babies a month or two to boost immunity.
The search for new ways to better understand this process, Sing Sing Way, a doctor of pediatric infectious disease at the Hospital Medical Center of Cincinnati Children in Ohio, wondered whether the transfer of immune adult cells could rev their immune system. Yet when he and his colleagues injected the fight against infection of cells from adult mouse spleens in 6 days old puppies, nothing happens: The puppies were just as vulnerable to harmful bacteria than the control animals. Probing deeper into this surprise, they found that the injected cells have simply stopped work in newborn animals. Then the Way group made the transplant, they reversed the mouse newborn adult immune cells that have been inactivated in puppies and found that they "lit" in adult animals. These experiences "told us it was not a problem with the neonatal cells themselves," says Way. On the contrary, he believes the environment is a newborn body, or an adult with a guided how the cells behaved.
others in the laboratory study of the gut microbiome Way, the constellation of healthy bacteria that fills our intestines. newborn mice, just like human babies are born " clean ", with little intestinal bacteria. Very quickly it changes. Way wonders if there might be a connection between this settlement and what looked like a deliberate suppression of the immune system in its mouse.
to find out, a group focused on immune cells that eventually develop into red blood cells and which express a surface receptor called CD71, which causes immunosuppression other cells. Knocking about 60% of these cells as CD71 much that their technology could handle-was followed by severe inflammation in the intestines of mice. Way and his colleagues also found that as the mice increased, fewer cells boasted CD71 receptors, suggesting the removal was not necessary. He theorizes that this is because the gut is colonized by this point.
The work, reported online today in Nature "adds a new and very important chapter" in the history of how the immune system develops, said Mike McCune, an immunologist at the University of California, San Francisco. immunosuppression, at least in newborn mice, appears to reflect a deliberate change in the balance of immune cells. the concept is certainly plausible, accepts Heather Jaspan, a specialist in pediatric infectious diseases and immunologist at the University of Cape Town and Seattle BioMed in Washington. She wonders about other cell types in addition to those receptor CD71 that may play a role. "It would be interesting to follow this issue with other studies of cause and effect," she said, finally nailing the specific immune suppression allows bacteria to colonize the gut without harming the newborn.
Much caution is whether that Way team observed held in human babies. the baby's immune system develops differently than a mouse, and Way is interested in search of CD71 cells in babies born around their due date, as well as those born prematurely. Very premature infants often die from a disease called necrotizing enterocolitis, a massive inflammation of the intestine. Way McCune and wonder if this resulted in part from a lack of CD71 cells in these babies-if, essentially, their immune systems are still fetal, not ready for natural colonization of intestinal bacteria happens after that they were born. In theory and far into the future, the researchers say, could receive preemies immune cells that would make them immune system more like a full-term baby, allowing their guts to stay healthy.
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