Passive Immunity

Passive immunity is achieved by the direct injection of antibodies or antiserum to defend against infection. This provides immediate, though temporary, protection from a specific disease-causing bacteria, virus or toxin to persons unable to produce antibodies. Newborn infants receive a natural passive immunity across the placenta; for the first few months of life, infants will have the same antibody protection as their mothers.

Passive immunity is often provided by the administration of immune globulin with specific antibodies after exposure when there isn't time for immunization and the development active immunity. In the case of Hepatitis B, the vaccination schedule takes place in three injections over a six-month period. If a person were exposed to Hepatitis B, the immune globulin would provide immediate protection.

Immune globulin with specific antibodies can be administered to treat diseases normally prevented by immunization. As in the case of tetanus, Clostridium tetani, the bacterium causing the disease is ubiquitous in soil and in the event of a puncture wound may infect the wound and cause the disease in persons who haven't been immunized.

Passive immunity can be provided when active immunization isn't practical or available. A situation when this would occur is after snakebite. Animal toxins are composed of proteins and because of this can produce an antibody response. The antiserum is made by immunizing animals with the venom to produce a variety of antibodies. When injected into a human after for example snakebite, the antibodies in the antivenin (or anti-venom) combine with the venom from the bite to render it ineffective. Different snakes produce different venoms, some are neurotoxic causing respiratory paralysis, or cytolitic, causing tissue and cell destruction.

Serum from one person with specific antibodies can be given to another person who doesn't have the antibodies, and the recipient will gain immunity for a short period of time, until the antibodies degrade. Intravenous Immune Globulin (IVIG) contains a wide variety of antibodies to provide a broad range of protection against illness. IVIG is produced with purification and viral inactivation from donated serum from a large pool of donors to contain millions of antibody specificities. Serum is the fluid in the blood containing the proteins with antibodies in three different globulins alpha, beta and gamma. Gamma globulin contains the most antibodies.

Complications may arise from the administration of these injections. The administration of anti-venins or globulins produced in animals may cause anaphylaxis, anaphylactoid reactions or serum sickness (the deposit [Page 1341]of antigen-antibody complexes most commonly in skin, joints, or the kidneys). Hypersensitive reactions are rare after administration of human immunoglobulins.