The Newborn Immune System And Immunological Benefits Of Breastmilk

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The Newborn Immune System and Immunological Benefits of Breastmilk

 

 

A newborn does not yet have a mature immune system and is often

unable to mount an effective immune response. Newborns are generally

protected by the antibodies they receive through the placenta before

birth and through their mother's breastmilk after birth. These

antibodies will be the same ones that are circulating in the mother's

system, which will include antibodies to the microorganisms in the

mother's home environment and other places she frequents. Therefore,

babies generally have antibodies to the germs in their own homes.

However, many of the germs in a hospital environment are foreign to

both the mother and the baby, so the baby will not have antibodies to

protect against these germs, and the baby cannot create its own

antibodies against these new germs. This problem can be mitigated by

making sure that the baby is touched minimally by people other than

the mother and the immediate family, who share a common germ pool.

 

 

The greatest infectious danger to a newborn in the hospital is the

prevalence of bacteria that have developed resistance or complete

protection against antibiotics. Antibiotics are no longer effective

against these " superbugs " , so there is no effective antibiotic

treatment for a " superbug " infection.

 

 

If a baby in the hospital develops an infection from one of these

" superbugs " , nothing other than prayer can help them.

 

 

Excerpts from Textbooks

 

 

From Williams Obstetrics, 19th Edition, p. 1281

 

 

A major mechanism for inducing infection subsequent to birth is from

those caring for the infant who may be colonized with the organism or

may passively transfer it from another infected infant.

 

 

Myles Textbook for Midwives, Bennett/Brown, Twelfth Edition

 

 

Immunological adaptations, p. 508

Neonates demonstrate a marked susceptibility to infections,

particularly those gaining entry through the mucosa of the

respiratory and gastro-intestinal systems. Localisation of infection

is poor, " minor " infections having the potential to become

generalised very easily.

The baby has some immunoglobulins at birth, but the sheltered intra-

uterine existence limits the need for learned immune responses to

specific antigens. There are three main immunoglobulins, IgG, IgA and

IgM, and of these only IgG is small enough to cross the placental

barrier. It affords immunity to specific viral infections. At birth

the baby's levels of IgG are equal to or slightly higher than those

of the mother. This provides passive immunity during the first few

months of life.

 

 

IgM and IgA do not cross the placental barrier but can be

manufactured by the fetus. Levels of IgM at term are 20% those of the

adult, taking 2 years to attain adult levels (elevation of IgM levels

at birth are suggestive of intra-uterine infection). This relatively

low level of IgM is thought to render the infant more susceptible to

enteric infections. IgA levels are very low and produced slowly

although secretory salivary levels attain adult values within 2

months. IgA protects against infection of the respiratory tract,

gastro-intestinal tract and eyes.

 

 

Breast milk, and especially colostrum, provides the infant with

passive immunity in the form of lactobacillus bifidus, lactoferrin,

lysozymes and secretory IgA among others.

 

 

Properties and Components of Breast Milk, p. 523

Anti-infective factors - During the first 10 days there are more

white cells per ml than there are in blood.

Macrophages and neutrophils are amongst the most common leucocytes in

human milk and they surround and destroy harmful bacteria by their

phagocytic activity.

 

 

Secretory IgA and interferon are important anti-infective agents

produced in abundance by lymphocytes in human milk.

 

 

Immunoglobulins IgA, IgG, IgM and IgD are all found in human milk. Of

these the most important is IgA, which appears to be both synthesised

and stored in the breast. It 'paints' the intestinal epithelium and

protects the mucosal surfaces against entry of pathogenic bacteria

and enteroviruses. It affords protections against E. coli,

salmonellae, shigellae, streptococci, staphylococci, pneumococci,

poliovirus and the rotaviruses.

 

 

Lysozyme is present in breast milk in concentrations 5000 times

greater than in cow's milk. It is a well known general anti-infective

agent and its activity appears to increase during lactation.

 

 

Lactoferrin is abundant in human milk but is not present in cow's

milk. It effects the absorption of enteric iron, thus preventing

pathogenic E. coli from obtaining the iron they need for survival.

 

 

The bifidus factor in human milk promotes the growth of Gram-positive

bacilli in the gut flora, particularly Lactobacillus bifidus, which

discourages the multiplication of pathogens. Babies who are fed on

cow's milk formula have Gram-negative (potentially pathogenic)

bacilli in their gut flora.

 

 

Nurse-Midwifery, Helen Varney, Second Edition, p. 419

 

 

Immune System Changes

The neonate has an impaired ability to react to invading organisms.

On a cellular level there is a decreased ability of leukocytes to

concentrate where necessary. These leukocytes are less bactericidal

and phagocytic. At the humoral level the newborn has low or

nonexistent levels of the immunoglobulin antibodies IgM, IgE, and

IgA. The neonate is born, however, with IgG antibodies acquired from

the mother, which confer protection from some specific diseases.

There is a slow rise of immunoglobulin levels after 3 months of age

to levels of older children.

 

 

Maternity and Gynecologic Care, Bobak, Jensen, Zalar, Fourth Edition,

p. 470

 

 

Immune System

All newborns and especially preterm newborns are at high risk for

infection during the first several months of life. During this

period, infection represents one of the leading causes of morbidity

and mortality. The newborn is unable to limit the invading pathogen

to the portal of entry because of a generalized hypofunction of the

inflammatory and immune mechanisms (Medici, 1983).

Resistance to infection (immunity) includes both non-specific and

specific protective mechanisms. Medici (1983) summarizes the

newborn's defense mechanisms as follows:

 

 

The term and preterm neonate has an increased incidence of infection

for the first 4 to 6 weeks of life. This reflects the immaturity of a

number of protective systems which significantly increases the risk

of infection in this patient population. Natural barriers such as the

acidity of the stomach or the production of pepsin and trypsin which

maintain sterility of the small intestine are not fully developed

until 3 to 4 weeks. The membrane protective IgA is missing from the

respiratory and urinary tracts, and unless the newborn is breast-fed,

it is absent from the gastrointestinal tract as well. The immune

system is in great part suppressed; possibly this is a mechanism for

preventing maternal recognition of paternal antigens with subsequent

reject of the fetus. Finally, the qualitative and quantitative

response of the inflammatory factors and sluggish responses of the

phagocytic cells [leave the baby vulnerable to infection].

 

 

These web pages were originally composed by Ronnie Falcao, LM MS, in

Sept., 1997.

 

 

They have been updated as new information has become available.

 

Contact Ronnie Falcao, LM MS