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Poor Immune Function May Play Role in Malnutrition, Researchers Suggest

FILE - A 5-year-old boy with severe malnutrition rests on a bed at the Aweil State Hospital in Northern Bahr El-Gazhal, South Sudan, Oct. 9, 2015

Experts say 45 percent of all child deaths in the world are associated with malnutrition and infections. Research in the last several years has begun to look at a possible link between increased risk of infections, caused by poor immune system function, and mortality among undernourished children.

In a review paper published in the journal Trends in Immunology, researchers at Queen Mary University of London and the Kenya Medical Research Institute presented evidence that suggests starvation alone is not the only cause of death among children who don’t have enough nutritious food to eat.

They said malnutrition could be the result of a process that begins with and is compounded by a malfunctioning immune system inherited from the previous generation, which leads to increased death from infection in the malnourished.

Aid organizations' efforts to treat malnutrition and wasting are often incomplete.

“There is some improvement with feeding interventions, but you don’t entirely reverse the negative effects of malnutrition, such as stunting, which is a very common outcome in children who are malnourished," said Claire Bourke, an immunologist at the Center for Genomics and Child Health at Queen Mary University. "They don’t grow as tall as they should.”

Researchers don’t know whether immune dysfunction causes malnutrition or the other way around. Either way, the immune dysfunction can be epigenetically imprinted by malnutrition, which affects gene expression. So, the baby of a malnourished mother could inherit an altered immune system, and there is growing evidence that impaired immunity may lead to malnutrition in the offspring, even if they have an adequate diet, according to experts.

Mouse models

At this point, researchers have a poor understanding about how the immune system and malnutrition are interrelated. They are beginning to tease out the relationship between the two using mouse models.

It is widely known that children who are severely malnourished endure a host of immune system problems. These include having fewer white cells for fighting off infection, fragile gut membranes that are easily penetrated by microbes, and defective lymph nodes — cradles where disease-fighting cells are formed.

Bourke is heartened by the notion that altering immune pathways could be a new target to reducing poor health due to over- and undernutrition.

Studies are underway in Africa to see whether something as simple as giving antibiotics or anti-inflammatory medication to malnourished children improves the health of a large percentage of the kids.

“And if the immune system provides new keys to reducing that huge burden of mortality and morbidity due to malnutrition, then I think it’s a really exciting possibility,” said Bourke.

The findings are adding to a new understanding of the immune system: In addition to fighting off infection, it plays a role in a well-functioning metabolism, the health of the nervous system, and growth, which is impaired by malnutrition.