Cleft lip surgery is classified a clean-contaminated surgery
because, although there are no infections at that moment, the location
puts it at increased risk. The mouth is widely considered the dirtiest part of the human body,
yet babies have surprisingly low infection rates following cleft lip and
Now, researchers have the first evidence that one reason may be the presence of what they call the SWAT team of immune cells.
They examined lip tissue removed during cleft lip repair of 13
babies at Children's Hospital of Georgia. They found innate lymphoid
cells, or ILCs, a type of immune cell that functions like a natural
antibiotic to recognize and attack invaders like bacteria. In the
average mouth, where hundreds of types of bacterium have been
documented, there is plenty to target.
‘The presence of SWAT team of immune cells may be responsible for the surprisingly low infection rates following cleft lip and palate surgery.’
"ILCs are newly discovered as one of our immune cells, but they are
really old. We had just missed them," said Dr. Babak Baban, immunologist
in the Department of Oral Biology at The Dental College of Georgia and
in the Department of Surgery at the Medical College of Georgia at
"Their presence helps explain why we don't have more surgical site
infections than we do," said Dr. Jack Yu, chief of pediatric plastic
surgery at MCG and director of the Craniofacial Center at CHOG.
Scientists began to report about ILCs in 2008 and 2009 and their
ability to defend against infection and aid wound healing. Like our
natural killer cells, they are essentially born ready for action. Other,
so-called adaptive immune cell types need to be educated on what to
attack, typically by exposure to it, and develop receptors and a memory
for these so-called antigens, said Baban, the study's corresponding
The need for education leaves babies with immature adaptive immune
systems for their first few months of life, said Baban, which is when
levels of ILCs appear highest. While present throughout life, it's early
on that ILCs appear particularly vital: "When you knock these guys out,
you are dead," Yu said of attempts to create animal models in which the
fast-reacting cells had been removed. Conversely, levels seem to drop
with age, possibly as adaptive immune cells mature and take on some of
their responsibility, Baban said.
Yu has been doing cleft lip and palate repair nearly 25 years, and
he and Baban decided to team up to explore the surprisingly low rates of
surgical site infection considering the amount of bacteria found in
even the cleanest, healthiest mouth. While the bacteria count would
support infection rates more like 5-7%, rates today are under 1%, said Yu, a study coauthor.
Their research found all three types of ILCs - types 1, 2 and 3 -
in the lip tissue, but mostly type 2, which is more good news since it
typically functions like the director of the SWAT team, Baban said.
"Type 2 basically dictates to the other cells how they should behave,
how they should function," he said of the always-hierarchical immune
While they were the first to document ILCs in the mouth, the
researchers weren't really surprised to find the cells there. Shortly
after birth, fast-acting ILCs appear to populate babies, particularly
concentrating on the alimentary canal, which is the path that food
follows and where their maturing immune system is housed, said Baban.
The cells gather in barrier surfaces like the mucosal lining of the
intestines, airways as well as skin, the body's largest organ, and
pretty much any place that comes in contact with outside substances from
food to water to other humans, Baban said.
The researchers' current and future studies include comparing cell
numbers in young and older healthy mice. Baban also is looking at the
potential role of these cells in a range of diseases from gum disease to
melanoma and traumatic brain injury with the long-term goal of giving
patients doses of these cells to better combat their disease. This will
include identifying which ILCs naturally fight which infection and/or
disease. A dose of these cells may even one day replace an antibiotic
before surgery and help combat the epidemic of antibiotic resistance,
Unlike manmade antibiotics, ILCs continue to recognize a bacterium,
for example, that morphs to escape the drug's attention. "Our
antibiotics are no good after two years. These cells have been around
billions of years and still are," Yu said.
The babies whose tissue was examined were an average of 6 months old
and had routine reconstructive surgery of their cleft lips. Five of the
babies also had a cleft palate that was later repaired. The researchers
immediately put the lip and mucosal tissue removed as part of the cleft
lip repair into a saline solution and took it to the lab for
Cleft lip and palate are the most common birth anomaly and occur in
about 1 in 700 births. Babies essentially have holes in these areas
where either formation was incomplete or tenuous and broke apart, Yu
said. Known risks include the mom smoking or drinking during pregnancy
and taking certain drugs, including anticonvulsants and some acne drugs.
Other surgeries classified as
clean-contaminated include oral, vaginal and anal procedures. Reported
infection rates for this classification of surgery average about 4%,
although prophylactic antibiotics can cut that rate in half,
the researchers write. Hand surgery is an example of an inherently clean
Depending on their severity, the birth defects can cause a range of
dysfunction, including trouble eating, drinking and speaking as well as
aesthetic concerns and related psychological problems. Yu, who is editor
of the Cleft Palate-Craniofacial Journal
, generally considers age four months an optimal time for surgical repair.