One of newborns' biggest vulnerabilities is largely invisible: In the weeks after birth, babies are especially susceptible to infection because their immune systems aren't fully functional. There are a handful of theories to explain this liability, and now a research team has added a new one to the list: Immune suppression in early life might help prevent inflammation in the infants' intestines as they become colonized by the helpful bacteria they need to stay healthy.
Newborns are more likely than older babies to catch, and die from, serious infections. The reason is fuzzy - indeed, there may be more than one explanation. One theory is that much like their brains, their lungs, and the rest of their bodies, infants' immune systems just haven't fully matured yet. Another is that both mothers-to-be and their in utero companions have suppressed immune systems, so that neither rejects the other. After birth, the thinking goes, it takes babies a month or so to boost their immunity.
Seeking new ways to better understand this process, Sing Sing Way, a pediatric infectious disease doctor at Cincinnati Children's Hospital Medical Center, wondered whether transferring immune cells from adults might rev up their immune systems. Yet when he and his colleagues injected infection-fighting cells from the spleens of adult mice into 6-day-old pups, nothing happened: The pups were just as vulnerable to harmful bacteria as control animals. Probing more deeply into this surprise, they found that the injected cells simply stopped functioning in the newborn animals. Then Way's group did the reverse transplant - they gave adult mice newborn immune cells that were inactivated in the pups and found that they "turned on" in the mature animals. These experiments "told us it wasn't a problem with the neonatal cells themselves," Way says. Rather, he believes, the environment - either a newborn body, or an adult one - guided how the cells behaved.
Others in Way's lab study the gut microbiome, the constellation of healthy bacteria that populates our intestines. Newborn mice, just like human babies, are born "clean," with little intestinal bacteria. Very rapidly that changes. Way wondered whether there might be some connection between this colonization and what looked like a purposeful suppression of the immune system in his mice.
To find out, his group focused on immune cells that eventually develop into red blood cells and that express a surface receptor called CD71, which causes immune suppression of other cells. Knocking out about 60 percent of these CD71 cells-as many as their technology could manage-was followed by significant inflammation in the intestines of the mouse pups. Way and his colleagues also found that, as the mice grew, fewer and fewer cells boasted CD71 receptors, suggesting the suppression wasn't needed. He theorizes that that's because the gut has been colonized by that point.
The work, reported online Wednesday in Nature, "adds a new and very important chapter" to the story of how the immune system develops, says Mike McCune, an immunologist at the University of California, San Francisco. Immune suppression, at least in newborn mice, appears to reflect a purposeful shift in the balance of immune cells. The concept is definitely a plausible one, agrees Heather Jaspan, a pediatric infectious disease specialist and immunologist at the University of Cape Town and at Seattle BioMed in Washington. She wonders about other cell types, in addition to those with CD71 receptors, that might play a role. "It would be interesting to follow this up with more cause and effect studies," she says, to nail down definitively that specific immune suppression allows bacteria to colonize the gut without harming a newborn.
One big caveat is whether what Way's team observed will hold up in human babies. A baby's immune system develops differently than that of a mouse, and Way is interested in looking for CD71 cells in babies born around their due date, as well as those born prematurely. Very premature infants often die of a condition called necrotizing enterocolitis, a massive inflammation of the intestines. Way and McCune wonder if that's driven partly by a lack of CD71 cells in these babies - if, essentially, their immune systems are still fetal, not ready for the natural colonization of gut bacteria that happens after they're born. In theory - and far in the future - say the researchers, preemies could receive immune cells that would make their immune system more like a full-term baby's, allowing their guts to stay healthy.
- Community News Network
VIDEO: Kentucky AG holds back tears, announces he won't defend marriage ban
In a tearful statement that went viral this week, Kentucky Attorney General Jack Conway announced that he would not defend his state's ban on gay marriage in court. Conway made the announcement after a federal judge ruled that Kentucky must recognize same sex marriages performed in other states. However, Gov. Steve Beshear said he will hire private attorneys to appeal the judge's order.
VIDEO: Will the NFL move the extra point to 42 yards?
The NFL's Competition Committee is reportedly in preliminary talks about spotting the ball at the 25-yard-line for point-after-touchdown attempts, which would make PATs 42 yards, according to NFL.com.
VIDEO: Bird smashes through airplane's windshield
A cockpit video camera captured the moment when a bird smashed through the windshield of a small plane.
VIDEO: Recall issued on Hot Pockets
Nestle has issued a recall of two varieties of Philly Steak and Cheese Hot Pockets because they may contain meat that's been recalled by the U.S. Department of Agriculture.
Will smart guns transform the gun industry?
One of California's largest firearm stores recently added a peculiar new gun to its shelves. It requires an accessory: a black waterproof watch.
VIDEO: Olympics turn hot, cold in Sochi
It is extraordinarily warm at the Sochi Olympics, but Team USA is running cold in all events but snowboarding.
Beatles fans take magical history tour 50 years later
Under the concrete ribs of the barrel-shell roof of a crumbling coliseum, the capital awaits the Beatles. Or, rather, the Beatles tribute band. The real thing is exactly 50 years gone on this Tuesday night, in this exact spot in Northeast Washington, and Washington must make do with imitation, with nostalgia, with the reverb of the past.
VIDEO: NFL hopeful Michael Sam opens up about sexuality
The defensive lineman from the University of Missouri spoke publicly about his sexual orientation and could become the first openly gay player in the National Football League.
Why Philip Seymour Hoffman's death is so scary
I cried when I heard about Philip Seymour Hoffman. The news scared me: He got sober when he was 22 and didn't drink or use drugs for the next 23 years.
When your tour operator flakes on you
American European Travel's nine-day ancient Turkey tour looked like the perfect birthday gift for David Olson's wife, Barbara. With stops in Istanbul, Ephesus and Pamukkale, it fulfilled a lifelong dream of visiting the old Ottoman Empire.
- More Community News Network Headlines
- VIDEO: Kentucky AG holds back tears, announces he won't defend marriage ban