Passively Acquired Immunity -
'Passive immunity' may also be acquired either by natural or artificial means. While passive immunity acquired by natural means, involves the transfer of antibodies from mother to her unborn child, through the placenta during the later part of pregnancy, passive immunity of the artificial type refers to the original production of antibodies in some other individual (human or lower mammal) followed by injection of these antibodies with the help of a needle or syringe.

Several drug manufacturing companies are involved in the large scale production of antibodies in horses and cows by active immunization.