Tuesday, June 28, 2016
Immune dysfunction: A cause and consequence of malnutrition
Malnutrition is one of the principal reasons for compromised immune function in under-five children. Hence, malnutrition is characterised by recurrent episodes of infection and chronic inflammation, which together imply an underlying immune defect. Immune dysfunction can lead to malnutrition-associated complications, such as malabsorption, increased metabolic demand, dysregulation of the growth hormone and the hypothalamo-pituitary axis, and greater susceptibility to infection.
Parental malnutrition paves the way to epigenetic modifications of infant immune and metabolic genes. There is an intimate association between the nutritional status and the diets of the mother and the infant. Infant infections, microbial colonisation of the gut, and T cell activation have been linked to breastfeeding practices and the development of gut microflora. The gastrointestinal tract forms the primary interface between dietary components, and microbes and the gut-associated lymphoid tissue.
Healthy gut development depends on commensal, pathogenic microbes and sensing dietary nutrients. Direct nutrient sensing enables the gut immune system to quickly adapt to environmental conditions, including micronutrient deficiencies. Clinical trials have shown that supplementing oral vitamin A during infancy consistently reduces diarrheal incidence, and mortality in children.
Recurrent infections, enteropathy, and inflammation may damage gut functioning, termed as environmental enteric dysfunction (EDD). Repeated exposure to enteric pathogens may cause EED, which affects the nutrient absorption process. Malnutrition also alters the functioning of hormones such as glucocorticoids and adipokines. Recurring infections due to immune dysfunction may also be related to diminished immunological memory responses to common pathogens in children.
The mechanistic way of reducing the extent of immune dysfunction is through the immune-metabolism pathway; altering energy usage in obesity and metabolic syndromes, drive immune activation and reduce inflammation in children. Additionally, longitudinal immune assessment and nutritional interventions help in reducing the timing, and extent of immune dysfunction in malnourished children.
News Source: Bourke CD, Berkley JA, Prendergast AJ. Immune dysfunction as a cause and consequence of malnutrition. Trends in immunology. 2016 Jun 30;37(6):386-98.