12.2L: In Vivo Testing

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In vivo testing using animal models of disease help discover new ways of solving complex health problems.

Learning Objectives

Describe how animals can be used for diagnostic antibody production

Key Points

In vivo testing is necessary for medical and research purposes. The medical field benefits from animal models to test the safety of drugs before they are used on patients. The research field benefits from in vivo testing by validating in vitro findings in vertebrates closest to humans.
The most used animal models are mice, rats, and other rodents.
In vivo testing is useful for the production of polyclonal antibodies applied in immunoassays and diagnostic immunology.

Key Terms

in vitro: In an artificial environment outside the living organism.
antiserum: a serum prepared from human or animal sources containing antigens specific for combatting an infectious disease
in vivo: Within a living organism.

In Vivo Testing

In vivo methods refer to the use of animals as a conduit to generate purified polyclonal antibody solutions ( antiserum ) for research purposes. Polyclonal antibodies are applied in immunological assays to diagnose disease.

In vivo testing follows strict guidelines and humane animal use ethics. The protocol for diagnostic antibody production in animals follows multiple steps. Animals are injected with microbes or antigenic fragments that elicit an immune response; the immune response is allowed to develop for 1-2 weeks, after which blood is harvested. This blood now contains antibodies created from the antigens that were introduced into the animals. Antibodies are purified from the serum to make antiserum or a purified antibody solution for one particular antigen.

Figure: **A white laboratory rat**: Animals are used in laboratory experiments to translate in vitro findings.

These preparations will produce multiple antibody types that recognize different epitopes on the antigen, hence the term polyclonal. Polyclonal antibodies have various applications in the clinic and in research laboratories. Animals are also used to model human diseases in the research field. They are useful vehicles to understand how our bodies work, find cures and treatments for diseases, test new drugs for safety, and evaluate medical procedures before they are used on patients.

Mice, and other rodents such as rats and hamsters, make up over 90% of the animals used in biomedical research. In addition to having bodies that work similar to humans and other animals, rodents are small in size, easy to handle, relatively inexpensive to buy and keep, and produce many offspring in a short period of time. In vivo testing remains a crucial step for the evaluation of in vitro experimental findings and the production of immunological solutions needed for the diagnosis of human diseases.