Passive Immunity and BioDefens
Immunization is a process of fortifying an individual’s immune system against an agent, typically disease-causing pathogen or a toxin. When the immune system is exposed to foreign molecules, this will trigger an immune response. Because of immunological memory, our immune system is also able to develop the ability to respond quickly to any subsequent encounter with the same agent, which is a function of the adaptive immune system – a subsystem which responds within 4-7 days to a previously encountered foreign molecule. The concept of exposing the body to a foreign agent in a controlled manner to artificially activate the immune system and impart the ability of a quick response to a subsequent encounter due to immunological memory is called active immunization.
Active immunization gives the body the ability to produce antibodies to counter the pathogen or a toxin on its own. The most common technique of active immunization is vaccination, a process of introducing a microorganism or a virus in a weakened, live or killed state, or proteins or toxins from that microorganism, triggering the body’s adaptive immunity. This allows the body to quickly respond to a next encounter with the same pathogen or toxin. Inoculation refers to a method where the body is exposed to a milder form of a disease to induce immunity. It originated as a method of preventing smallpox, where dried smallpox macules were used to induce a generally milder form of the disease, which still induced full immunity to the disease. Compared to vaccination, it is inferior due to significantly higher risk – vaccination does not cause disease, even in its milder form, while inoculation does.
Passive immunization is a process of introducing antibodies into the body directly, rather than imparting on the body the ability to produce them. This still imparts immunity, however, because this immunity is not caused by the body’s immune system, it will only last as long as the introduced antibodies as present in the organism. This is called transient immunity. Antibodies have been used for the prevention and treatment of various diseases for centuries (Keller, 2000). Immunization by the administration of antibodies is a very efficient way of obtaining immediate, short-lived protection against infection or the disease-causing effects of toxins from microbial pathogens or other sources.
Due to its rapid action, passive immunization is often used to treat diseases caused by infection or toxin exposure. In bacterial diseases, antibodies neutralize toxins, facilitate opsonization, and, with complement, promote bacteriolysis. In viral diseases, antibodies block viral entry into uninfected cells, promote antibody-directed cell-mediated cytotoxicity by natural killer cells, and neutralize virus alone or with the participation of a complement. Prior to the discovery of antibiotics, antibodies were the only available treatment for a significant number of infectious diseases.
American BioDefense Institute