Passive immunity refers to short-term protection from disease resulting from transfer of ready-made antibodies (immunoglobulins). This is in contrast to active immunity Active Immunity in Animals Active immunity refers to immunity to a disease resulting from longterm humoral and cell-mediated memory responses by the immune system in the host in response to an antigen. This is in contrast... read more , which refers to immunologic defense by an animal's own immune system.
Passive immunity may be acquired naturally (eg, maternally derived antibodies transferred to neonates Failure of Transfer of Passive Immunity in Large Animals Large animal neonates are born with limited energy reserves and are considered immunocompetent but immunologically naive at birth (ie, agammaglobulinemic). Thus, ensuring the provision of good-quality... read more via the placenta or colostrum) or artificially (eg, via donor serum or monoclonal antibodies generated through the use of cloned cell lines).
Polyclonal Antibodies in Animals
Antibodies from one animal, such as those produced in response to vaccination, can be transferred to another. Serum from a donor animal can be administered to susceptible animals to confer immediate but short-lived protection.
Immune globulins may be produced in cattle against anthrax Anthrax , in dogs against distemper Canine Distemper virus, and in cats against panleukopenia Feline Panleukopenia virus. Their most important role is in protection against toxigenic organisms, such as tetanus Tetanus in Animals Tetanus is caused by the neurotoxin produced by Clostridium tetani , which is found in soil and intestinal tracts and usually introduced into tissues through deep puncture wounds. The... read more , botulism Botulism in Animals Botulism most commonly results from ingestion of toxin in food. The usual source of the toxin is decaying carcasses or vegetable material. Clinical signs are caused by flaccid muscle paralysis... read more , or Clostridium perfringens Clostridium difficile and C perfringens Infections in Animals Clostridium difficile is a large, gram-positive, anaerobic, spore-forming motile rod and is the major cause of antimicrobial-associated colitis in humans. C difficile–associated... read more . They can also be used in the treatment of snake envenomation. These immune globulins are generally produced in young horses by a series of inoculations.
Monoclonal Antibodies in Animals
In a normal immune response, antibodies are produced by diverse plasma cell populations and are thus said to be polyclonal. Although these antibodies all combine with a specific organism, they are a heterogeneous mixture of proteins that react to different epitopes of that organism.
Homogeneous antibodies that react to a single epitope can be generated through the use of cloned cell lines called hybridomas; these monoclonal antibodies represent an alternative source of passive immunity.
Whereas the earliest monoclonal antibodies were made by mouse hybridomas (and thus consist of mouse antibodies), molecular engineering techniques now permit them to be altered to match the recipient species. For example, a caninized monoclonal anti-IL-31 antibody may be used to block severe itch in dogs with atopic dermatitis Atopic Dermatitis .
Monoclonal antibody use has increased greatly in humans. These antibodies are mainly directed against inflammatory cytokines such as tumor necrosis factor and IL-1. They are primarily used for the control of chronic inflammatory diseases, such as rheumatoid arthritis and systemic lupus.
Monoclonal antibodies are also used to combat many human cancers either by attacking cancer cells directly or by enhancing cytotoxic T-cell responses. Caninized monoclonal antibodies are being increasingly used against cancer in dogs.