Active and passive immunity

 Active immunity and passive immunity are two types of immune responses that protect the body from pathogens, but they differ in how they are acquired and how long they last.

Active Immunity

Active immunity occurs when the immune system is exposed to an antigen and generates a response, leading to the production of memory cells that offer long-term protection. This type of immunity can develop naturally or through vaccination.

• Natural Active Immunity: This happens when a person is exposed to a pathogen, becomes infected, and the immune system responds. For example, if someone gets the flu, their body will recognize the virus in the future and produce antibodies more quickly if they are exposed again.

• Artificial Active Immunity (Vaccination): Vaccines stimulate the immune system by introducing a weakened or inactivated form of a pathogen or its proteins. The body generates a memory response without causing illness. For example, the measles vaccine helps the body develop immunity to the measles virus.

Advantages of Active Immunity:

• Long-lasting: Because memory cells are formed, active immunity can last for years or even a lifetime.
• Adaptive: The immune response adapts to the specific pathogen, offering a tailored defense.

Passive Immunity

Passive immunity occurs when antibodies are transferred from one individual to another. In this case, the recipient’s immune system does not produce memory cells, so the immunity is temporary. There are two forms of passive immunity:

• Natural Passive Immunity: This happens when antibodies are passed from mother to child, either through the placenta during pregnancy or through breast milk. These antibodies offer immediate protection to the baby but do not last long.

• Artificial Passive Immunity: Involves the transfer of antibodies, usually through injections of immune globulins. This is used for immediate, short-term protection. For instance, after exposure to rabies or tetanus, a person may receive an injection of antibodies to neutralize the pathogen.

Advantages of Passive Immunity:

• Immediate protection: It provides quick defense in situations where the body’s immune response would take too long.
• Temporary: While the antibodies offer protection, they are eventually broken down, and the immunity does not last for long.

Summary of Key Differences:

Aspect	Active Immunity	Passive Immunity
How Acquired	Exposure to pathogen or vaccine	Transfer of antibodies from another person
Onset	Takes time to develop	Immediate
Duration	Long-lasting, often years or lifelong	Short-term, usually weeks to months
Memory Cells	Yes, memory cells are produced	No, memory cells are not produced

Both forms of immunity play crucial roles in protecting the body, but active immunity is key for long-term disease prevention, while passive immunity is essential for immediate protection.