The role of the immune system and HMO in protecting children’s weak immune system


The immune system is a “shield” that protects the body against invading agents such as viruses, bacteria or parasites. A healthy immune system will repel the invasion of harmful agents, helping children avoid diseases and support a healthy development for children.

The importance of immunity to human body

The immune system is essential for life. Without the immune system, the body will easily be attacked by bacteria, viruses, parasites… The immune system presents all around the body and is related to many types of diseases. cells, organs, proteins, tissues and keep the body safe when exposed to pathogens.

Everyone’s immune system is different, but as a general rule, the immune system becomes stronger as one matures. That’s why teenagers and adults tend to get sick less than children.

The immunity is the “shield” which protects the body from harmful factors (Photo: Tcimedicine)

The immunity is the “shield” which protects the body from harmful factors (Photo: Tcimedicine)

There are three types of immunity in humans called innate immunity, active immunity and passive immunity:

Innate Immunity: We are all born with some level of immunity to external diseases. The human immune system, similar to that of many animals, attacks foreign pathogens. This innate immunity includes our body’s external barriers – the first line of defense against pathogens – such as the skin and mucous membranes of the throat and intestines. If pathogens seek to evade the innate immune system, adaptive or passive immunity will occur.

Active immunity: When we are exposed to disease or vaccinated, we build a library of antibodies to different pathogens. This is sometimes called immunological memory because our immune system remembers previous pathogens.

Passive immunity: This type of immunity is “borrowed” from another source, but does not last indefinitely. For example, the baby receives antibodies from the mother through the placenta before birth and in breast milk after birth. This passive immunity protects the baby from certain infections in the first years of life.

Weak immature immune systems make children susceptible to infections

An immune system in newborns is strong thanks to the antibody system received while still in the fetus. However, antibodies began to decline sharply over the next 6 months. Children need to be breastfed immediately and exclusively until 6 months of age, because this is a passive source of antibodies to maintain immunity.

From 6 months of age onwards, the antibodies transmitted by the mother to the child are greatly reduced. At this time, the child’s immune system is not yet complete, it is not until 3 – 4 years old that this system can fully produce antibodies. Antibodies help fight infections. The time between the interference of  passive and active immune systems between 6 months and 3 years old is the time when children become susceptible to infections such as diarrhea and respiratory infections or allergies.

Weak immune systems make children susceptible to infections (Photo: Sg.Theasianparent)

Weak immune systems make children susceptible to infections (Photo: Sg.Theasianparent)

When the body’s immune system is weakened, resistance decreases, causing the rate of children to get sick increases, especially when the weather changes. Children can get some of the following diseases when their immune system is weakened:

Respiratory diseases: The respiratory system in young children is not fully developed, the airways are short, breathing many times per minute will create conditions for disease-causing viruses and bacteria to easily penetrate. Respiratory diseases that young children are susceptible to are: Acute pharyngitis; rhinitis, flu, laryngitis and acute croup, complications of pneumonia… For children with bronchitis, complications of pneumonia, acute pharyngitis… if not treated promptly, there can be can lead to dangerous complications. Bacteria are considered the cause of the disease if fever, cough, and painful swallowing do not limit themselves or become worse after 5-7 days.

Acute laryngitis and croup: Common in children from 6 months to 6 years old, most common in 2-year-old children. The disease begins with common symptoms of nasopharyngitis, the child begins to have hoarseness, mute voice, wheezing, noisy breathing (also known as stridor), and concavity of the sternum and chest. Children cough a lot, can have difficulty breathing, hyperventilate, pull accessory respiratory muscles, sweat, turn pale, lethargic and die if not treated promptly.

Pneumonia: Occurs at all ages, mainly caused by bacteria, especially Hib bacteria and pneumococcus. The disease manifests itself as soon as possible with signs of abnormally fast breathing, coughing with wheezing if there is a lot of mucus secretion in the respiratory tract. Some children may have high fever, tired breathing, and lethargy. The disease can be fatal for children if not detected early and treated aggressively.

VA inflammation: Found in all ages, especially children 2 months to 2 years old. Children’s runny nose and persistent nasal congestion are typical signs of the disease.

Acute rhinosinusitis: The disease is similar to acute rhinosinusitis, but symptoms tend to get milder and then get worse after a week. Children have stuffy nose and persistent runny nose. Nasal mucus turns milky white, green or yellow. Children often cry a lot; If children can talk, they may complain of headaches, pain behind the eye sockets, heavy face, and dry throat.

Gastrointestinal diseases: In children (especially children in the first 5 years of life), the intestinal tract is not fully developed, enzyme activity is weak, the endocrine system, circulatory system and liver, kidneys function are not yet fully developed. When the immune system is weakened, cold weather is a favorable condition for pathogen bacteria, viruses and parasites to develop.

Children with digestive disorders: Digestive disorders are a condition of abnormally increased intestinal motility, food metabolism and absorption disorders, causing abdominal pain and changes in defecation. When children have digestive disorders, they will experience inconvenience in daily activities. Due to changes in toileting problems, children often have abdominal pain, bloating, and discomfort.

Young children are susceptible to digestive disorders because their digestive system is not structurally completed. Long-term digestive disorders prevent children from fully absorbing nutrients for healthy development. As a result, children often suffer from malnutrition. Slow physical development and underdeveloped immune system.

Diarrhea: This is one of the most common gastrointestinal diseases in children. The main cause of this problem is that the child’s intestines are infected with a virus or attacked by some types of bacteria. Typical symptoms of diarrhea are children defecating at least 3-4 times a day, the stool is quite loose and often mixed with mucus. Along with that, symptoms children may face such as abdominal pain, dehydration, loss of electrolytes…

Diarrhea exists in two main forms, acute and chronic, which parents should monitor carefully. When having diarrhea, a child’s body loses water extremely quickly. If this condition is not treated promptly, it can threaten the child’s life and health.

Dysentery: Mainly caused by Amoebic parasites and Shigella bacilli, people with dysentery have very little stool, but it is accompanied by mucus and blood, along with symptoms of fever, abdominal pain, and always feeling sick, always wanting to go to the toilet, gradually, the child weakens, struggles, falls into a coma and then dies.

The main risk of amoebic dysentery is that it becomes chronic and long-lasting. In addition, Amoeba parasites can invade the liver causing liver abscesses. Shigella type often causes dysentery in children. This type is not chronic and does not cause liver abscesses, but acute complications can cause death within 24 hours.

HMO – Precious nutrients protect children’s bodies from harmful agents

Breast milk is the best source of nutrition to ensure the health of newborns because it contains complete nutrition as well as all the biologically active ingredients necessary for optimal development in the first months of life.

Breast milk mainly consists of water, lactose, lipids, and milk proteins, which are especially rich in complex carbohydrates, collectively known as Human Milk Oligosaccharides (abbreviated as HMO). HMO helps create a “barrier” layer to protect children’s health against attacks from bacteria in the environment.

HMO is the main ingredient in breast milk, besides water, lactose, lipids and proteins (Photo: Experts Community Network)

HMO is the main ingredient in breast milk, besides water, lactose, lipids and proteins (Photo: Experts Community Network)

According to the study “Functional properties and HMO production technology” by author Ma Bich Nhu (Van Lang University – Ho Chi Minh City)3, HMO is a complex sugar that occurs naturally in breast milk and provides many beneficial functions for infants. Breast milk contains more than 150 structurally distinct HMOs, divided into three types: neutral fucosylated, neutral non-fucosylated, and acidic or sialylated. Sialylated HMOs and 2-fucosyllactose (2- FL) have an impact on brain development and children’s learning ability. Other non-acidified HMOs are the preferred substrates for bifidobacteria and HMOs act as decoys to prevent the adhesion of viral or bacterial pathogens to receptors on cells.

HMO acts as an anti-adhesive agent: Many pathogens caused by viruses, bacteria or protozoan parasites need to adhere to the surface of epithelial cells to proliferate, and in some cases can penetrate and cause diseases. Typically, the initial attachment is on the epithelial cell surface (glycans) also known as the glycocalyx. While these glycans are conjugated to proteins or lipids and HMOs resemble some glycan structures and act as soluble front-facing receptors (decoys) that prevent the binding of pathogens to epithelial cells4. Pathogens can no longer stick to the cell surface and will be washed out without causing illness to the newborn5.

HMOs act as anti-bacterial agents: HMOs may protect infants from pathogens by acting as prebiotics that give beneficial bacteria a growth advantage and by acting as anti-corrosion agents in terms of interaction between microorganisms and host6. Additionally, HMOs may have a more direct way to control pathogens. Some studies have concluded that group B streptococcus (Streptococcus agalactiae) is no longer able to reproduce in the presence of HMO. As a typical example, GBS (Group B streptococcus – group B streptococcus) is one of the leading neonatal pathogens affecting approximately 1/2000 newborns in the US7, genital tract also increases the probability of urinary tract infections (UTIs) in pregnant women. Some studies on GBS use glycosyltransferases to incorporate specific HMOs into their cell membranes, which then block GBS proliferation like some commercially available antibiotics. HMOs can protect the body from pathogens caused by viruses, bacteria, or protozoa. As another example, Candida albicans is a fungus common to the infant’s gut, causing the majority of invasive fungal diseases in premature infants and being widely associated with life-threatening intestinal disorders such as intestinal necrosis and intestinal perforation8. HMO treatment significantly reduced Candida albicans infiltration of human small intestinal epithelial cells (pIECs) in a dose-dependent manner.

HMO changes the response of epithelia and immune cells: HMO also indirectly affects bacteria by changing the response of host cells. Some studies have concluded: “HMO can regulate the apoptosis, proliferation, and differentiation of intestinal epithelial cells”9, “HMO has also been shown to change the gene expression of intestinal epithelium cells, leads to changes in cell surface glycocalyx”10. Thus, HMOs not only influence bacteria-host attachment by acting as soluble receptors but also alter the expression of glycocalyx receptors by reprogramming epithelial cell tissues.

Thus, HMO plays an important role in the human immune system. The results of the clinical research “HMO and the development of the immune system” (Human Milk Oligosaccharides and Immune System Development11) by a group of authors at the University de Granada – Spain also showed that HMO has a supportive effect on protecting children’s weak immune system from harmful agents. Therefore, in the first years of life, breast milk is a source of quality nutrition for children to supplement natural HMO, thereby improving the body’s immune function.

Build an “immune barrier” to protect children’s bodies from harmful agents with 2’FL-HMO

As mentioned above, HMO is the third most abundant nutrient in breast milk with more than 150 different HMOs. Among them, 2’FL-HMO (2′-Fucosyllactose) is the most common type of HMO in breast milk, accounting for the largest amount, up to 30% of the total HMO content in breast milk, and plays an extremely important role, helps children stay healthy and increase their resistance.

2’FL-HMO (2’-Fucosyllactose) is the most common HMO in breast milk (Photo: Freepik)

2’FL-HMO (2’-Fucosyllactose) is the most common HMO in breast milk (Photo: Freepik)

According to research by the Scientific Council of the European Food Safety Authority (EFSA), among the many types of HMO found in breast milk, 2’FL-HMO is one of two types of HMO that have been assessed and evaluated for applicability and safety to fortify with food for children. 2’FL-HMO possesses the following great benefits:

Improve intestinal immune system: About 70% of the immune system is located in the intestinal tract, so the best way to increase children’s resistance is to take care of intestinal health. In the child’s immune system, there are always beneficial bacteria that help the child’s body fight against harmful agents from outside. However, it is impossible to guarantee 100% that harmful bacteria are absent. Therefore, if the beneficial bacteria are not nourished, they will not be strong enough to fight harmful bacteria. At this time, 2’FL-HMO acts as a Prebiotic, becoming a “food” source for beneficial bacteria, stimulating their growth. From there, the baby’s digestive system and intestines are stronger, effectively absorbing nutrients for the body.

Prevents the adhesion of harmful bacteria: 2′-FL HMO also helps fight adherent bacteria and viruses, preventing them from sticking to the intestinal wall. Thanks to that, bacteria are eliminated from the body through the digestive tract, helping children limit the risk of infection. Without 2’FL-HMO, these virus groups will adhere tightly to the intestinal tract, causing infections in children.

Enhance brain development in children: 2’FL-HMO also acts as a source of sialic acid (N-acetylneuraminic acid, a constituent of Ganglioside – a molecule concentrated in nerve endings, has the function of transmitting nerve signals, helping to improve memory and brain formation in children) for the development of the nervous system. Thanks to that, children develop comprehensive awareness and, the ability to absorb and learn faster.

Children’s weak immature immune systems are at risk of infection. According to recommendations from experts, parents should make efforts to maintain breast milk supply in the first years of life to fully supplement HMO for their baby.

In cases where children are not breastfed to absorb this nutrient, parents can choose nutritional products containing HMO, especially 2’FL-HMO. In addition, parents also need to supplement probiotics through food to strengthen the immune system, support the digestive process, and prevent digestive disorders in children. When children start solid foods, parents need to feed them lots of fruits, vegetables, and grains. Bananas and asparagus are natural vegetables rich in beneficial bacteria, contributing to strengthening children’s resistance. Foods rich in vitamin C such as oranges, tangerines, cherries, grapes, grapefruit, apples, kiwis, and bananas… help prevent virus invasion and improve the ability of cells to kill bacteria.


  1. Goto, K., et al. (2010). Chemical characterization of oligosaccharides in the milk of six species of New and Old World monkeys. Glycoconjugate Journal, 27(7), 703-715.
  2. Morrow, A.L., et al. (2005). Human-milk glycans that inhibit pathogen binding protect breast-feeding infants against infectious diarrhea. The Journal of Nutrition, 135(5), 1304-1307.
  3. Newburg, D.S., G.M. Ruiz-Palacios, and A.L. Morrow. (2005). Human milk glycans protect infants against enteric pathogens. Annual Review of Nutrition, 25,37-58. 
  4. Julio Plaza-Díaz, Luis Fontana, Angel Gil. (2018) Human Milk Oligosaccharides and Immune System Development.
  5. Ross, S.A., et al. (2016). The role of oligosaccharides in host-microbial interactions for human health. Journal of Clinical Gastroenterology, 50, s 131 -S132.
  6. Marcobal, A. and J. Sonnenburg. (2012). Human milk oligosaccharide consumption by intestinal microbiota. Clinical Microbiology and Infection, 18,12-15.
  7. Trung tâm Y tế quận Gò Vấp. “Cơ chế hoạt động của hệ miễn dịch), 2022.
  8. Cổng thông tin điện tử ngành Y tế tỉnh Hà Tĩnh. “Các bệnh thường gặp khi hệ miễn dịch của trẻ bị suy giảm”, 2022. 
  9. Mã Bích Như, “Tính chất chức năng và công nghệ sản xuất HMO”, 2022.
  10. Trung tâm Kiểm soát bệnh tật Hà Tĩnh, “4 cách giúp trẻ tăng sức đề kháng”, 2018.
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