New research suggests that immune-suppressing cells may be a cause of infection vulnerability in newborn infants – and they are the same cells that allow good bacteria to safely colonize an infant’s intestines.

Researchers from Cincinnati Children’s Hospital Medical Center say their findings could “prompt a major shift” in how medical professionals view the threat of neonatal infections, and could have an important bearing on research into new prevention strategies.

The researchers note that at present, the view of medical professionals is that newborn infants are vulnerable to infection because they have immature or underdeveloped immune system cells. But the researchers say their new discovery challenges this belief.

To reach their findings, published in the journal Nature, the researchers conducted a series of laboratory tests in mouse models and human blood cells.

They looked specifically at suppressive cells called CD71+. These are precursors of mature red blood cells.

The researchers found that these cells are enriched in newborn mice and human umbilical cord blood. This is to stop the immune response from overreacting as newborn infants adapt to their new environment.

An enzyme called arginase-2 is expressed by the CD71+ cells, the researchers explain, and this is essential in order to suppress immune cells.

The researchers say this process plays an important role in the development of infants’ intestines, as it stops inflammation in response to colonizing bacteria that helps digestion and other related functions.

To test whether immune suppression in newborns goes beyond the intestines, the researchers extracted immune system cells from adult mice and transferred them into newborn mice to see if this would boost their immunity when exposed to infection.

However, the researchers found that protective immune system cykotines in the adult cells were not produced, so immunity was not enhanced in the newborn mice.

Immune system cells from newborn mice were also transferred into adult mice that were exposed to infection. The researchers found that the immune cells from the newborn mice produced protective cykotine TNF-alpha. This helps increase the protective response of the immune system against infection.

Explaining their findings, Sing Sing Way, of the Division of Infectious Diseases at Cincinnati Children’s Hospital, says:

“The first few days after birth represent a critical developmental period when a baby’s immune system must adapt to many new stimulants. This includes environmental microbes that are not present in the womb, but immediately colonize tissues such as the intestine and skin.”

Our findings fundamentally change how we look at neonatal susceptibility to infection by suggesting it is caused by active immune suppression during this developmental period, as opposed to the immaturity of immune cells.”

The researchers note that the process of CD71+ immune suppression is vital for the intestines to build up healthy bacterial colonization, and this is more important than the threat of neonatal infection.

However, they emphasize that further research is warranted in order to create new strategies for the protection of newborn infants against infection while still allowing the CD71+ cells to assist in developing healthy intestines.

They note that controlling or modulating CD71+ immune suppression is a possible strategy, but that much more research is needed before any findings can be applied to human newborns.

Medical News Today recently reported on a study suggesting that newborn infections may be linked to later behavioral problems.