ABSTRACT
Passive immunization is the administration of preformed antibodies, usually IgG, either intravenously or intramuscularly. These may be derived from individuals who have high antibody titers to particular microbes and can thus provide rapid protection against infections such as Diphtheria, rabies, or those caused by Clostridium species. They are also very useful in the event of accidental exposure to certain pathogens such as hepatitis B. Passive immunization is also used to provide protection in immunocompromised individuals who are unable to make appropriate antibody responses or in some instances incapable of making any antibody at all, that is, in severe combined immunodeficiency. Antibodies given to immune-deficient patients are usually of the IgG class and are derived from pooled normal plasma. These antibodies must be given on a continuous basis, ideally every three weeks, because they are continuously catabolized and are only effective for a short period.
