When a person or animal receives a vaccination to protect against a specific disease, the protection is in the form of antibodies. The vaccine is composed of the disease organism, or some part of it, and when administered to the recipient results in production of antibodies by the recipient’s lymphocytes (B-cells). The immunity conferred by the vaccination can last for as short as a few months to as long as many years, depending on the organism. For example, it is recommended that dogs be vaccinated against canine parvovirus annually, whereas humans vaccinated against tetanus only require re-vaccination every ten years.
One of the major uses of laboratory animals is for the production of antibodies and other components of the immune response. Immunized animals are used to evaluate the effectiveness of specific vaccines. Specific cells of the immune system, such as lymphocytes and macrophages, are routinely collected and studied to evaluate their role in animal defense against infections, disease, and cancer. The antibody produced in response to immunization is often used as a critical component of a non-animal laboratory test; for example, in immunoserology tests used to diagnose many diseases.
The response of animals to an injection of an antigen is the same as that of humans to a vaccine; that is, they produce antibodies. Virtually any laboratory animal species can be used to produce antibodies. The choice of species often relates to the properties of the antigen. Animals are given a series of injections of an antigen preparation, usually after a pre-immunization blood sample has been collected to be sure the animal does not already have antibodies that may complicate the study. About three weeks after the series of injections, blood is again collected, and the serum is evaluated for the presence of antibody. If the level of antibody is not adequate for research purposes, additional antigen injections, or boosters, are given. The serum antibody can be stored in a freezer for years, thus providing an ongoing supply of the needed experimental reagent. In cases in which an animal’s antibody response is exceptional, the animal may be kept at the animal facility for a long period of time. During this time it receives occasional booster immunizations, and periodic blood collections are taken from it. The animal thus provides the research investigator with a continuous supply of an essential antibody.