Neonatal Immune System Adaptation Processes

Neonatal Immune System Adaptation Processes

Neonates’ WBC responds slowly and inefficiently when the body is invaded with microorganisms. This is due to the immaturity of the hypothalamus and inflammatory responses. Because of the immaturity of the immune system, neonates are susceptible to pathogens which do not generally affect older children.

Full-term neonates receive antibodies from the mother during the last trimester of pregnancy. When an infant is breastfed, the mother continues to give antibodies to the infant. This is called passive immunity. These immunoglobulin help protect the newborn from infection. At birth there are about 55-80% of antibodies present in the newborn’s body.

Immunoglobulin G (IgG)

There is only one immunoglobulin that passes or crosses that placenta, the IgG. IgG starts to cross the placenta at the first trimester of pregnancy.  However, the largest amount of IgG transfer is noted during the third trimester of pregnancy. Thus, a preterm neonate is more susceptible to infection that a full-term infant.

This type of immunoglobulin provides the fetus a passive immunity to possible bacterial and viral infections. However, the passive immunity it provides is only temporary. The immunity gradually disappears at about 6 to 8 months of life. The gradual disappearance of passive immunity, leads to the gradual production of larger quantities of immunoglobulin to replace the IgG from the mother.

Immunoglobulin M (IgM)

IgM is the first immunoglobulin produced by the body when the neonate is distressed, has acquired an infection or is challenged. When a newborn is exposed to environmental antigens, production of IgM rapidly increases. This type of immunoglobulin provides protection from gram-negative bacteria. IgM cannot cross the placental barrier.  In cases where large amount of IgM is found in the placenta, possible exposure to infection in the utero is probable.

Immunoglobulin A (IgA)

Another immunoglobulin produced by the infant’s body is called the Immunoglobulin A (IgA). Neonates are susceptible to infections in the gastrointestinal (GI) and respiratory systems. IgA is vital in providing protecting of those systems.

Another important function of IgA is limiting the absorption of antigenic protein the diet of an infant. A particular form of IgA is present in the colostrum and breast milk. This is the main reason why breastfed infants have more immune protection than the formula fed babies.

Daisy Jane Antipuesto RN MN

Currently a Nursing Local Board Examination Reviewer. Subjects handled are Pediatric, Obstetric and Psychiatric Nursing. Previous work experiences include: Clinical instructor/lecturer, clinical coordinator (Level II), caregiver instructor/lecturer, NC2 examination reviewer and staff/clinic nurse. Areas of specialization: Emergency room, Orthopedic Ward and Delivery Room. Also an IELTS passer.

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