Scientists link immune system's natural killer cells to infant liver disease

July 22, 2009
Pranavkumar Shivakumar, Ph.D., (standing), and Jorge Bezerra, M.D., of Cincinnati Children's Hospital Medical Center, analyze a bile duct tissue sample from a 7-day-old mouse. Their study in the Journal of Clinical Investigation links an over-reactive response by natural killer cells in the immune system to the onset of biliary atresia in infants, a disease in which blocked bile ducts can cause severe liver damage and death. Credit: Cincinnati Children's Hospital Medical Center

Scientists have linked an overactive response by one of the immune system's key weapons against infection - natural killer, or NK, cells - to the onset of biliary atresia in infants, a disease where blocked bile ducts can cause severe liver damage and death.

Researchers at Cincinnati Children's Hospital Medical Center also report that blocking a gene that helps NK cells attack tissues lessens damage and may be a way to treat the most common cause of chronically progressive in . The study, to be published in the Aug. 3 , is posted online on the journal's website.

"Our findings underscore the developing immune system's role in causing injury to bile ducts soon after birth, and they have implications for developing new therapies to block the disease by targeting certain cells or pro-inflammatory circuits," said Jorge A. Bezerra, M.D., the study's senior investigator and research director of the Division of Gastroenterology, and Nutrition at Cincinnati Children's.

"The next steps for translating these findings into clinical application would include pre-clinical trials of biologics to halt disease progression by blocking the Nkg2d receptor and depleting NK cells at the time biliary atresia is diagnosed," he added.

Very little is known about the cause of biliary atresia, although it has been traced to the immune system responding to an infection in the liver and bile ducts. Surface tissues inside the bile ducts are damaged, which in turn allows to block the duct and the ongoing accumulation of fibrotic tissue. Biliary atresia affects about one in every 15,000 babies.

The current frontline treatment is surgery to remove and replace obstructed bile ducts with sections of the child's intestine. Without surgery, bile cannot enter the intestines to aid digestion, and instead backs up into and damages the liver. Corrective surgery is successful 65 to 85 percent of the time and is not considered a cure, although it can allow babies to have several years of fairly good health. In more severe cases, children may require a liver transplant.

To better understand the disease's apparent link to the developing and still immature infant immune system, researchers in this study analyzed the livers of infants diagnosed with biliary atresia. They discovered elevated populations of NK cells in the bile ducts. The NK cells over-expressed genes involved in creating substances that are cytotoxic, or toxic to living cells. This finding led the research team to experiment with a mouse model of biliary atresia.

In the mouse experiments, the scientists used a rotavirus infection to induce biliary atresia in newborn mice. Similar to what was observed in diseased human infant livers, the researchers found that active NK cells were the most abundant cells populating the mouse livers and bile ducts at the time of obstruction. Furthermore, they discovered that NK cells rely on the receptor gene, Nkg2d, to make contact with and attack bile duct surface cells by attaching to the Nk2d protein, which resides on the membranes of bile duct cells. Once that contact is established, NK cells break down the membranes of bile duct surface cells, leading to tissue damage.

When researchers blocked the Nkg2d receptor and depleted the number of NK cells, it prevented damage to bile duct surface tissues, even with the presence of rotavirus infection. The continuity of the mouse pup bile ducts was maintained, bile was able to flow from the liver to the intestines, and the animals grew well into adulthood without liver-related symptoms.

Source: Cincinnati Children's Hospital Medical Center (news : web)

Related Stories

Recommended for you

Hibernating ground squirrels provide clues to new stroke treatments

November 17, 2017
In the fight against brain damage caused by stroke, researchers have turned to an unlikely source of inspiration: hibernating ground squirrels.

Age and gut bacteria contribute to multiple sclerosis disease progression

November 17, 2017
Researchers at Rutgers Robert Wood Johnson Medical School published a study suggesting that gut bacteria at young age can contribute to multiple sclerosis (MS) disease onset and progression.

Molecular guardian defends cells, organs against excess cholesterol

November 16, 2017
A team of researchers at the Harvard T. H. Chan School of Public Health has illuminated a critical player in cholesterol metabolism that acts as a molecular guardian in cells to help maintain cholesterol levels within a safe, ...

Prototype ear plug sensor could improve monitoring of vital signs

November 16, 2017
Scientists have developed a sensor that fits in the ear, with the aim of monitoring the heart, brain and lungs functions for health and fitness.

Ancient enzyme could boost power of liquid biopsies to detect and profile cancers

November 16, 2017
Scientists are developing a set of medical tests called liquid biopsies that can rapidly detect the presence of cancers, infectious diseases and other conditions from only a small blood sample. Researchers at The University ...

FDA to crack down on risky stem cell offerings

November 16, 2017
U.S. health authorities announced plans Thursday to crack down on doctors pushing stem cell procedures that pose the gravest risks to patients amid an effort to police a burgeoning medical field that previously has received ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.