Antibodies transfer from mother to fetus though placenta is example of which type of immunity?

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2023

Explanation

Passive immunity is the transfer of ready-made antibodies from one individual to another.
In this case, the fetus receives pre-formed Immunoglobulin G (IgG) antibodies from the mother across the placenta.
The fetus's immune system is not actively involved in producing these antibodies.
This provides immediate but temporary protection to the newborn for the first few months of life.

Option A: Active immunity requires the individual's own immune system to produce antibodies in response to an antigen. The fetus is receiving antibodies, not producing them.
Option C: Herd immunity refers to community-level protection, not an individual's immune status. It describes how a vaccinated population can protect unvaccinated individuals.
Option D: Cellular immunity is mediated by T-cells and phagocytes, not antibodies (which are part of humoral immunity).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Types of Immunity as background academic context rather than a clinical decision trigger.
Understanding passive immunity is crucial for neonatal care. The protection from maternal antibodies wanes after a few months, which is why the infant vaccination schedule begins at 6-8 weeks of age.
Maternal vaccination (e.g., Tdap vaccine for tetanus, diphtheria, and pertussis) during pregnancy boosts the level of specific IgG antibodies transferred to the fetus, providing critical protection against diseases like whooping cough in early infancy.
What if? If a mother has an autoimmune disease where her IgG antibodies attack certain cells (e.g., Rh incompatibility), these harmful autoantibodies can also cross the placenta and cause disease in the fetus, such as hemolytic disease of the newborn.

How to Approach the Question

First, identify the key elements in the question: 'antibodies transfer', 'mother to fetus', and 'placenta'.
Recall the definitions of the different types of immunity.
Active immunity involves the body making its own antibodies.
Passive immunity involves the body receiving pre-made antibodies.
The scenario describes the fetus receiving antibodies from the mother. This directly matches the definition of passive immunity.
Differentiate this from herd (community-level) and cellular (T-cell mediated) immunity, which do not fit the scenario.

Concept Tested & Keywords

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E6 Microbiology Applied AnjuDhir 3e Part 2 p. 88-90

E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart A (pp 26-201 of 604) p. 95-97

E6 Pharmacology Nursing Lilley 11e Part 3 p. 148-150

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