Artificially acquired active immunity is immunity gained from receiving an immunization with an antigen, explains Dr. Gary E. Kaiser with The Community College of Baltimore County. Injecting an antigen into the body provokes the immune system to produce antibodies and B-memory cells specific to that antigen.
Dr. Kaiser explains how B-memory cells allow the body to remember an antigen. If the body is exposed to the antigen again, the B-memory cells cause immediate production of the necessary antibodies to protect against that antigen. Active immunity is longer-lived than passive immunity, which is generated from antibodies originating from outside the body.