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Gastrointestinal host defence: importance of gut closure in control of macromolecular transport
Insights
Newborns have an immature gut barrier, making them vulnerable to infections and allergies. Human milk provides essential passive immunity and protective factors, crucial for infant gut health and development.
Area of Science:
- Gastroenterology
- Immunology
- Neonatal Medicine
Background:
- The gastrointestinal tract develops a mucosal barrier to prevent harmful substances like bacteria, toxins, and antigens from penetrating the gut.
- Newborns, especially premature infants, have an underdeveloped mucosal barrier, increasing vulnerability to infections and inflammatory conditions.
- Harmful intraluminal substances can trigger inflammatory and allergic reactions, potentially leading to serious diseases like necrotizing enterocolitis and sepsis.
Purpose of the Study:
- To highlight the importance of the mucosal barrier in newborns.
- To explain the consequences of an immature mucosal barrier in neonates.
- To emphasize the protective role of human milk in compensating for the underdeveloped intestinal defense system.
Main Methods:
- Review of existing literature on neonatal gastrointestinal development and immunology.
- Analysis of the components and functions of the intestinal mucosal barrier.
- Examination of the protective elements present in human milk.
Main Results:
- The neonatal mucosal barrier is incompletely developed at birth, leaving infants susceptible to gut penetration by harmful substances.
- This vulnerability can lead to infections, hypersensitivity reactions, immune complex formation, and severe diseases.
- Human milk contains antibodies, leucocytes, and other factors that actively protect the infant's gut.
Conclusions:
- The immature mucosal barrier poses significant risks to newborns, necessitating external protective mechanisms.
- Human milk is a vital source of passive immunity and protective factors, essential for defending the vulnerable newborn gut.
- Breastfeeding is crucial for mitigating the risks associated with an underdeveloped intestinal defense system in neonates.
Abstract:
An important adaptation of the gastrointestinal tract to the extrauterine environment is its development of a mucosal barrier against the penetration of harmful substances (bacteria, toxins and antigens) present within the intestinal lumen. At birth, the newborn infant must be prepared to deal with bacterial colonization of the gut, with formation of toxic byproducts of bacteria and viruses (enterotoxins and endotoxins) and with the ingestion of antigens (milk proteins). These potentially noxious substances if allowed to penetrate the mucosal epithelial barrier under pathological conditions can cause inflammatory and allergic reactions which may result in gastrointestinal and systemic disease states. To combat the potential danger of invasion across the mucosal barrier the infant must develop an elaborate system of defence mechanisms within the lumen and on the luminal mucosal surface which act to control and maintain the epithelium as an impermeable barrier to uptake of macromolecular antigens. These defences include a unique immunological system adapted to function in the complicated milieu of the intestine as well as other non-immunological processes such as a gastric barrier, intestinal surface secretions, peristaltic movement and natural antibacterial substances (lysozyme, bile salts) which also help to provide maximum protection for the intestinal surface. Unfortunately, during the immediate postpartum period, particularly for premature and small-for-dates infants, this elaborate local defence system is incompletely developed. As a result of the delay in the maturation of the mucosal barrier newborn infants are particularly vulnerable to pathological penetration by harmful intraluminal substances. The consequences of altered defence are susceptibility to infection and the potential for hypersensitivity reactions and for formation of immune complexes. With these reactions comes the potential for developing life-threatening diseases such as necrotizing enterocolitis, sepsis and hepatitis. Fortunately, 'nature' has provided a means for passively protecting the 'vulnerable' newborn against dangers of a deficient intestinal defence system, namely human milk. It is now increasingly apparent that human milk contains not only antibodies and viable leucocytes but many other substances which can interfere with bacterial colonization and prevent antigen penetration.