Passive Immunity

Passive immunity is the transfer of ready-made antibodies to a person or animal, conferring humoral immunity without the recipient's own immune system generating it. It occurs naturally when maternal antibodies cross the placenta to a fetus, and can be induced artificially by giving blood products containing high levels of antibodies against a pathogen or toxin, as in immunoglobulin therapy or antiserum therapy. Passive immunization is used when infection risk is high and there is not enough time for the body to mount its own response, or to reduce symptoms of an ongoing or immunosuppressive disease, including for people unable to synthesize their own antibodies.