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Taking care of a newborn is no easy task and adding to that, infants have a tendency to fall sick too often. Parents have always been worried and wonder why their infants fall sick so often, and in an attempt to help them quell their worries, researchers at the University of Michigan Health System have conducted a study to find the roots of the problem.

It is a common notion that the way infants take their time to learn to walk and talk, it also takes some time for them to develop their immunity to be able to fight against viral infections. However, a U-M study suggests that the natural ability to fight infection is present from a very early period.

The study findings have revealed that if certain cells, which slow down the growth of essential immune cells are blocked, it could perhaps lead to an improvement in an infant's response to infection.

"What happens at early age is that natural killer cells, like many other immune cells, do not complete their functional maturation until adulthood," said study senior author Yasmina Laouar, Ph.D., assistant professor in the U-M Department of Microbiology and Immunology, in the press release.

"During this time we are left with an immature immune system that cannot protect us against infections, the reason why newborns and infants are more prone to infection," she said.

Why there is a deficiency in the natural killer cell response in infants' immunity has not been well understood.  This study by immunologists at the U-M demonstrates the role of a cell called transforming growth factor beta (TGF-β) that can explain the exact reason behind the same.

According to the study, which was conducted on infant mice, the production of natural killer cells is controlled by TGF-β, which is produced in the bone marrow.

In mice, it was found that the maturation of natural killer cells progressed much faster in the absence of TGF-β signaling.

In the absence of TGF-β, an adult mouse had 10 times more mature natural killer cells.

"Our overall goal was to determine the factors that constraint the production and maturation of natural killer cells early in life," says Laouar. "To our surprise, we discovered that natural killer cells can complete maturation as early as 10 days of age if TGF-β signaling is blocked."

According to the authors, although it is tempting to propose the functional inactivation of TGF-β signaling in infants to encourage early maturation of natural killer cells, further study is still required.

The study was published online ahead of print in Nature Immunity.