Which immunoglobulin protects the newborn against enteric infection?

Appeared in: MP CHO -2021 (Shift 1st)

Explanation

Secretory IgA is the primary immunoglobulin that provides passive immunity to the newborn's gastrointestinal tract.
It is abundantly found in colostrum and breast milk, which are transferred from the mother to the infant.
IgA functions by coating the mucosal surfaces of the gut, which prevents enteric (gut-related) pathogens from attaching and causing infections.

Option B: IgD is primarily found on the surface of B lymphocytes, where it acts as a B-cell antigen receptor. It is not involved in providing passive immunity to the newborn against infections.
Option C: IgE is the immunoglobulin responsible for mediating allergic reactions (Type I hypersensitivity) and is also involved in the defense against parasitic worms (helminths).
Option D: IgM is the first antibody produced by the fetus's own immune system in response to an infection. It does not cross the placenta from the mother. Therefore, its presence in a newborn indicates an active or recent intrauterine infection, rather than passive protection.

Clinical Relevance

Nursing practice connection: Knowing Passive immunity in newborns and the role of immunoglobulins helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses should strongly encourage early initiation of breastfeeding (within the first hour) to ensure the infant receives colostrum, which is exceptionally rich in IgA.
Educating parents about the benefits of exclusive breastfeeding for the first six months is crucial for maximizing protection against common childhood illnesses like diarrhea and respiratory infections.
What if? If a mother cannot breastfeed, the infant will not receive passive mucosal immunity from IgA. While formula provides necessary nutrition, it lacks maternal antibodies, making the infant more susceptible to enteric infections.

How to Approach the Question

First, identify the key terms in the question: 'immunoglobulin,' 'protects newborn,' and 'enteric infection.'
Recognize that 'enteric' specifically refers to the gastrointestinal tract or intestines.
The question is asking about a form of passive immunity, where protection is transferred from mother to child, not produced by the newborn itself.
Recall the different classes of immunoglobulins and their primary roles and methods of transfer:
IgG: Crosses the placenta, providing systemic (blood) immunity.
IgA: Transferred through breast milk, providing mucosal (gut, respiratory) immunity.

Concept Tested & Keywords

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E6 Obstetrics Williams p. 29-50

E6 Microbiology Essentials Sastry 4e Part 1 pp. 149-151, 150-152

Practise the full MP CHO -2021 (Shift 1st)

Attempt every question from this paper in a timed mock, then review the full solution for each one.