Immune System in Neonates

The immune system of neonates is immature and not fully functional, their susceptibility to infections and ability to respond appropriately is impaired. However, neonates are protected against infections through passive immunity; conferred through IgG and IgA antibodies, transferred from the mother through the placenta during the last trimester of pregnancy, and through the breastmilk during lactation, respectively.¹ By 2 to 3 months of age, the levels of the antibodies begin to drop and the neonate’s immune system starts to develop.²

Breast Milk: A Key Ingredient in Development

Breast milk serves a valuable source through which the immunological memory is transferred from the mother to the infant. It contains several biologically active, antimicrobial peptides (AMPs), like defensins and cathelicidin, and immune-modulatory compounds that support active and passive immunity during the early years of life. Breast milk components like probiotics and oligosaccharides also play a role in the developing intestinal microbiome of the infant, which is critical in immune system development.¹ 

Role of Breast Milk in Nutrition and Immunity

There are several components present in breast milk that influence the development of the immune system. These are immunoglobulins, human milk oligosaccharides (HMO), lactose, lactalbumin, long-chain polyunsaturated fatty acids (LC-PUFAS), vitamins (A, E, C), interleukins, lactoferrin, lysozyme, lactoperoxidase, food antigens from the maternal diet, soluble CD14 receptors, TLR2, tumor necrosis factor (TNF-), defense cells (macrophages, neutrophils), and probiotics.⁴

Breastfeeding provides infants with protection against respiratory and gastrointestinal infections and is associated with reduced risk for inflammatory diseases such as asthma, atopy, obesity, and inflammatory bowel disease.⁴

• The U.S. Dietary Guidelines for Americans and the American Academy of Pediatrics recommend exclusive breastfeeding for about 6 months, and then continuing breastfeeding while introducing complementary foods until your child is 12 months old or older.⁵

Nutrients, Their Function and Impact of Its Deficiency

Breastfeeding and nutritional supplements play key role in growth and immunity development in infants up to 2 years of age. Nutritional deficits during this period leads to impaired growth and poses the risk of obesity, hypertension, diabetes, etc. in adulthood. Neonates and infants up to 2 years of age should be provided adequate healthy nutrients to ensure proper development of the immune system.²