Passive immunity is achieved through?

NIMHANS Nursing Officer - 2021

Applied Microbiology & Infection control

Easy

Appeared in: NIMHANS Nursing Officer - 2021

Explanation

Natural passive immunity involves an infant receiving pre-formed antibodies from the mother, rather than producing them independently.
This transfer occurs through two main pathways, making both sources listed correct.
During pregnancy, IgG antibodies cross the placenta, providing systemic immunity to the fetus.
After birth, secretory IgA antibodies are transferred through breast milk (especially colostrum), providing mucosal immunity to the newborn's gut and respiratory system.
Therefore, the combination of both placental and breast milk transfer constitutes the full scope of natural passive immunity for an infant.

Option A: This option is incomplete. While breast milk is a crucial source of passive immunity (providing IgA), it is not the only source. It omits the significant transfer of IgG antibodies that occurs via the placenta during pregnancy.
Option B: This option is also incomplete. The placenta is a primary route for passive immunity (transferring IgG), but it is not the sole source. It neglects the important role of breast milk in providing IgA antibodies after birth.
Option D: This option is incorrect because both the mother's breast milk and the placenta are well-established and critical pathways for the transfer of passive immunity to the infant.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Natural Passive Immunity as background academic context rather than a clinical decision trigger.
Nurses must educate expectant and new mothers on the benefits of breastfeeding, emphasizing that colostrum is rich in antibodies and provides vital protection against infections.
Understanding passive immunity is crucial when caring for preterm infants, as they are born with lower levels of transplacental IgG, making them more susceptible to infections.
What if? If a mother is unable to breastfeed, the infant will miss out on the mucosal protection provided by secretory IgA. While they still have placental IgG, they may be more vulnerable to gastrointestinal and respiratory infections. In such cases, counseling on formula safety and hygiene is critical.

How to Approach the Question

First, identify the core concept in the question, which is 'passive immunity'.
Recall the definition of passive immunity: receiving ready-made antibodies, not making them yourself.
Differentiate between natural and artificial passive immunity. The options (mother's milk, placenta) point towards natural immunity.
Consider the different stages of infant development. Before birth, the fetus is connected via the placenta. After birth, the infant can be fed breast milk.
Recall that antibodies are transferred during both stages: IgG across the placenta and IgA through breast milk.
Conclude that since both are valid methods of transferring passive immunity, the option 'Both of them' is the most complete and correct answer.

Concept Tested & Keywords

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