What is the difference between active and passive immunity?

Active immunity is when the body produces its own antibodies, while passive immunity is when antibodies are given from an external source.

Active immunity is a type of immunity that results from the production of antibodies by the immune system in response to the presence of an antigen. This can occur naturally when a person is exposed to bacteria or viruses, or artificially through vaccines. In both cases, the body recognises the foreign substance and produces antibodies to fight it. This process takes time, but the immunity is usually long-lasting because the immune system 'remembers' the antigen and can mount a quick response if it encounters the same antigen again.

On the other hand, passive immunity is the short-term immunity that results from the introduction of antibodies from another person or animal. This can occur naturally, such as the antibodies a baby receives from its mother through the placenta or breast milk, or artificially, such as the injection of antiserum, which contains antibodies from another person or animal. Passive immunity provides immediate protection, but the body does not develop memory, therefore the patient is at risk of being infected by the same pathogen later.

In summary, active immunity involves the body's own production of antibodies and is usually long-lasting, while passive immunity involves the introduction of antibodies from an external source and is usually temporary. Both types of immunity are crucial for protecting the body from diseases, but they function in different ways and have different advantages and disadvantages.