AIIMS Raipur NO - 201…: Which immunoglobulin can cross the placenta and can provide passive immunity to the newborn?

AIIMS Raipur NO - 2019 (Shift-1)

Applied Microbiology & Infection control

Easy

Appeared in: AIIMS Raipur NO - 2019 (Shift-1)

Explanation

IgG is the only immunoglobulin isotype that can pass through the human placenta, a process known as transplacental transfer.
This transfer is facilitated by its relatively small molecular weight and specific receptors on placental cells.
Maternal IgG provides the fetus and newborn with 'natural passive immunity', protecting them from infections that the mother has immunity against.
This protection is critical during the first few months of life, as the infant's own immune system is still developing.

Option B: IgE is primarily involved in mediating allergic reactions (Type I hypersensitivity) and responding to parasitic worm infections. It does not cross the placenta.
Option C: IgM is a large pentameric molecule, making it too big to cross the placental barrier. It is the first antibody produced in a primary immune response.
Option D: IgA is the main immunoglobulin found in mucosal secretions, including saliva, tears, and most importantly for a newborn, breast milk (especially colostrum). It provides local immunity but does not cross the placenta.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Placental transfer of immunoglobulins and passive immunity as background academic context rather than a clinical decision trigger.
The transfer of maternal IgG is vital for protecting newborns from common pathogens. The majority of this transfer occurs in the third trimester, placing premature infants at a higher risk for infections due to lower levels of received antibodies.
A nurse's role includes educating expectant mothers on the importance of vaccinations (like Tdap) during pregnancy, which boosts their IgG levels and consequently enhances the passive immunity transferred to the baby.
What if? If a newborn is born prematurely at 30 weeks gestation, the nurse should recognize that the infant has received significantly less maternal IgG compared to a full-term infant. This makes the premature baby more susceptible to infections, necessitating stricter infection control measures and close monitoring.

How to Approach the Question

First, identify the key concepts in the question: 'immunoglobulin', 'cross the placenta', and 'passive immunity to the newborn'.
This is a factual recall question. Access your knowledge about the five major classes of immunoglobulins (IgG, IgA, IgM, IgE, IgD).
Recall the primary function and unique characteristics of each class, specifically focusing on their ability to be transferred from mother to child.
Remember the mnemonic 'GAMED' for the immunoglobulins. IgG is the most abundant and the 'Go-getter' that 'Goes' across the placenta.
Eliminate the other options based on their known functions: IgA (secretory, in breast milk), IgM (primary response, too large to cross), and IgE (allergic reactions).
Select the option that correctly identifies the immunoglobulin responsible for transplacental passive immunity.

Concept Tested & Keywords

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