Passive immunity

Overview of Passive Immunity

• Passive immunity refers to the immunity that occurs when the body receives antibodies from an external source, rather than producing them itself.
• Key to distinguish between active immunity, where the body’s own immune system is triggered to produce antibodies.

Sources of Passive Immunity

• Two primary sources: received naturally through the placenta or through breast milk, or acquired artificially via injections.
• Natural Passive immunity: The mother’s antibodies are transferred to the foetus during pregnancy via the placenta and also via the colostrum and breast milk after birth.
• Artificial Passive immunity: This involves injection of antibodies. Often used in response to specific types of infection or severe allergic reactions.

Duration and Effectiveness

• Offers immediate, short-term protection. This is in contrast to active immunity (which takes time to develop but is long lasting).
• Passive immunity will only last as long as the antibodies remain in the system.

Potential Risks

• There can be risks associated with passive immunity. For instance, an allergic reaction to foreign antibodies can occur.
• This type of immunity can also interfere with response to vaccines, potentially making them less effective.

Practical Applications

• Passive immunity can be very useful in scenarios where a person is at immediate risk of infection. In such cases, waiting for the immune system to respond could be dangerous.
• Examples include treatment for rabies, tetanus, and snake bites, where antivenom (containing antibodies) may be given immediately after exposure.

Conclusion

• Passive immunity provides immediate protection but is temporary. It is an important part of the immune system’s response to infectious diseases, particularly in cases of immediate threat.