Active immunity is the protection against disease through the production of antibodies by the immune system in response to the presence of an antigen. This can occur naturally through infection or artificially through vaccination.
Passive Immunity: Short-term immunity provided by antibodies from another source, such as maternal antibodies or antibody-containing treatments.
Antigen: A substance that triggers an immune response, leading to the production of antibodies.
Memory Cells: Specialized immune cells that remember a specific pathogen and enable a rapid response upon re-exposure.