Question

Which of the following is true regarding passive and active immunity? A. Active immunity requires weeks to build, whereas passive immunity is acquired immediately. B. Active immunity is short-lived, whereas passive immunity is long-lived. C. Active immunity may be acquired during pregnancy through the placenta. D. Passive immunity may be acquired through vaccination.

Short answer

A. Active immunity requires weeks to build, whereas passive immunity is acquired immediately.

Step-by-step solution

Understand Passive Immunity

Passive immunity involves the transfer of antibodies from one organism to another. This type of immunity provides immediate protection but is usually short-lived. Common examples include the transfer of maternal antibodies through the placenta to the fetus, or the use of antibody-containing treatments.

Understand Active Immunity

Active immunity occurs when the body's immune system is exposed to a pathogen, either through infection or vaccination, and generates its own immune response. This process takes time to build up but usually provides long-lasting protection.

Analyze the Options

Consider each statement: A. Correct. Active immunity does take weeks to develop, whereas passive immunity is immediate.B. Incorrect. Active immunity is typically long-lived, while passive immunity is short-lived.C. Incorrect. Passive, not active, immunity is acquired through the placenta during pregnancy.D. Incorrect. Vaccination leads to active immunity, not passive immunity.

Select the Correct Answer

By analyzing the options, it is clear that Option A is the correct statement regarding passive and active immunity.

Key concepts

Passive Immunity

Passive immunity is a form of immunity where antibodies are transferred from one individual to another. This happens naturally, such as when maternal antibodies are passed to a fetus through the placenta. It can also occur artificially through treatments that contain antibodies.
This type of immunity provides immediate protection against disease. However, it is short-lived because the recipient's immune system does not develop its own response. Examples of passive immunity include:

• Transferring maternal antibodies through the placenta or breast milk to a newborn.
• Administering immunoglobulin treatments to boost the immune system during an infection.

In summary, while passive immunity acts quickly to protect against infections, it does not provide long-term resistance.

Active Immunity

Active immunity involves the body’s own production of antibodies in response to the presence of a pathogen. This can be through natural exposure to a disease-causing agent or through vaccination.
When the immune system encounters a pathogen, it takes time to recognize and mount a defense. The process involves:

• Recognition of the pathogen by immune cells.
• Activation of T-cells and B-cells (types of white blood cells).
• Production of antibodies specific to the pathogen.

This immune response takes a few weeks to fully develop, but it usually offers long-lasting protection. Unlike passive immunity, active immunity involves memory cells that remember the pathogen and respond more robustly upon future exposures.
Examples include recovering from an illness like measles or receiving vaccines like the flu shot.

Antibodies

Antibodies are proteins produced by the immune system to recognize and neutralize pathogens such as bacteria and viruses. These Y-shaped molecules are crucial players in both passive and active immunity.
In passive immunity, antibodies are externally sourced and transferred into the body. This provides immediate but temporary defense. In active immunity, the body generates its own antibodies in response to antigen exposure, enabling long-term protection.
Functions of antibodies include:

• Neutralizing pathogens directly.
• Clumping pathogens together for easier removal.
• Activating other immune cells to destroy the pathogen.

Each antibody is specific to a particular antigen, which allows the immune system to target infections precisely and effectively.

Vaccination

Vaccination is a method of stimulating active immunity by introducing a harmless form of a pathogen to the body. This prepares the immune system to recognize and respond to the actual pathogen if encountered in the future.
Vaccines may contain:

• Weakened forms of pathogens (live attenuated vaccines).
• Killed or inactivated pathogens.
• Parts of a pathogen, like proteins or sugars.
• Genetic material that instructs cells to produce a pathogen-specific antigen.

The goal of vaccination is to train the immune system without causing the disease. This results in the formation of memory cells, providing long-term protection. Examples of diseases preventable by vaccination include polio, measles, and COVID-19.