Passive Immunity

Passive Immunity is a form of immunity that is transferred from one individual to another, providing immediate protection against a specific pathogen or toxin. Unlike active immunity, which is acquired through vaccination or natural infection and involves the production of antibodies by the recipient's own immune system, passive immunity involves the transfer of pre-formed antibodies from a donor to a recipient. Passive immunity can be acquired naturally or artificially. In natural passive immunity, antibodies are transferred from a mother to her foetus during pregnancy through the placenta, or from a mother to her infant through breast milk. These maternal antibodies provide temporary protection to the newborn against certain infectious diseases until their own immune system matures and begins producing antibodies independently.

Artificial passive immunity, on the other hand, involves the administration of pre-formed antibodies derived from human or animal sources. This can be achieved through the injection of immune serum or purified immunoglobulins obtained from individuals who have been previously immunized or infected with the target pathogen. These antibodies provide immediate, short-term protection against the specific pathogen. Passive immunity is often used as a prophylactic or therapeutic measure to prevent or treat infectious diseases, particularly in situations where active immunization is not feasible or when immediate protection is required. For example, passive immunization with immune globulin preparations is commonly used to prevent or mitigate the severity of diseases such as hepatitis A, hepatitis B, rabies, tetanus, and varicella (chickenpox).
In addition to infectious diseases, passive immunity can also be used to treat certain autoimmune disorders, such as immune thrombocytopenic purpura (ITP) and Kawasaki disease, as well as toxin-mediated conditions, such as botulism and diphtheria.