What is the difference between passive and active immunity?

Passive immunity is acquired from outside the body, while active immunity is developed by the body itself.

Passive immunity is the transfer of antibodies from one individual to another, providing immediate protection against a specific pathogen. This can occur naturally, such as when a mother passes antibodies to her baby through breast milk, or artificially, such as through the injection of pre-formed antibodies (immunoglobulins). Passive immunity is short-lived, as the transferred antibodies eventually degrade and are eliminated from the body.

Active immunity, on the other hand, is developed by the body's own immune system in response to exposure to a pathogen. This can occur naturally, such as when a person contracts a disease and their immune system produces antibodies to fight it off, or artificially, such as through vaccination. Active immunity is long-lasting, as the body retains memory cells that can quickly produce antibodies if the same pathogen is encountered again in the future.

Both passive and active immunity provide protection against infectious diseases, but they differ in their mechanisms and duration of protection. Understanding these differences is important in developing effective strategies for preventing and treating infectious diseases.