Question 25

A mother passes antibodies to her child through breast milk.

Passive immunity is characterized by the transfer of antibodies from one individual to another, and this process is exemplified when a mother passes antibodies to her child through breast milk, providing immediate protection against antigens.

A) After primary exposure to an antigen, memory T cells remain to respond to a secondary exposure.

This option describes the mechanism of active immunity rather than passive immunity. Memory T cells are generated after exposure to an antigen and are crucial for a robust response upon re-exposure, but they do not involve the transfer of antibodies.

B) Exposure to a virus leads to the production of antibodies that can bind to the virus.

While this statement is true regarding the immune response, it pertains to active immunity where an individual produces their own antibodies in response to an infection. It does not describe passive immunity, which involves receiving antibodies from another source.

C) Immunization leads to the activation of B-cell proliferation.

This option also relates to active immunity. Immunization prompts the immune system to produce its own antibodies through B-cell activation and proliferation, rather than transferring pre-formed antibodies, which is the hallmark of passive immunity.

D) A mother passes antibodies to her child through breast milk.

This option accurately describes passive immunity as it involves the transfer of maternal antibodies to the infant, providing immediate protection against infections without requiring the child’s immune system to produce its own antibodies.

Conclusion

The correct answer, D, clearly illustrates the concept of passive immunity through the maternal transfer of antibodies, offering immediate protection to the infant. All other options incorrectly describe mechanisms related to active immunity, wherein the immune system generates its own response, thereby failing to align with the definition of passive immunity.