Explain how active immunity and passive immunity differ.

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1. Active immunity occurs when the body's immune system is stimulated to produce its own antibodies and memory cells in response to exposure to a pathogen or a vaccine. Passive immunity, on the other hand, involves the direct transfer of antibodies from another source, such as maternal antibodies passed through breast milk or antibodies given via injection.
2. Active immunity provides long-term protection because the immune system creates memory cells that can recognize and respond to the pathogen in the future. Passive immunity, however, offers short-term protection since no memory cells are produced, and the transferred antibodies degrade over time.
3. Active immunity can be acquired naturally through infection or artificially through vaccination. Passive immunity is acquired naturally through maternal transfer (e.g., during pregnancy or breastfeeding) or artificially through antibody injections (e.g., immunoglobulin therapy).
4. Active immunity requires time to develop because the immune system needs to recognize the pathogen, activate immune responses, and produce antibodies. Passive immunity provides immediate protection since the antibodies are already formed and ready to act.
5. Active immunity is generally more effective for long-term disease prevention, while passive immunity is used in situations where immediate protection is needed, such as exposure to a toxin or a rapidly progressing infection.

Key Concepts

Active Immunity

Active immunity occurs when an individual's immune system is exposed to a pathogen and produces its own antibodies in response. This can happen through natural infection or vaccination. The immunity developed is usually long-lasting, as the body retains a memory of the pathogen, allowing for a quicker response upon future exposures.

Passive Immunity

Passive immunity involves the transfer of antibodies from one individual to another, providing immediate but temporary protection. This can occur naturally, such as when a mother passes antibodies to her baby through breast milk, or artificially, through antibody-containing blood products. Unlike active immunity, passive immunity does not involve the recipient's immune system generating a response.

Immunological Memory

Immunological memory refers to the ability of the immune system to remember past infections and respond more effectively upon re-exposure to the same pathogen. This is a key feature of active immunity, as memory cells are created after an initial exposure, enabling a faster and stronger immune response in subsequent encounters. In contrast, passive immunity does not create immunological memory, as the transferred antibodies are eventually degraded.