VMC 221: Veterinary Immunology and Serology (1+1)

GENERAL CRITERIA IN SELECTION OF LAB ANIMALS

Choice of the animal

• Animals generally employed for production of antibodies are rabbits, sheep, goats, donkeys and horses. The rabbits are most commonly used,  due to the simplicity and low cost of their maintenance compared to other animals.
• Rabbit raised antiserum is a good source of antibody ((precipitin) in precipitation reaction.

Sex and age of animal

• The sex of the animal is irrelevant except in the case of animals that share cages, usually mice. Male mice are more aggressive and tend to injure one another, which can lead to opportunistic infections that divert the immune response.
• Other animals generally have a poorer response to injected antigens because their immune system has been engaged by so many other environmental antigens that their capacity to respond to new ones is limited.
•  Thus, in the case of rabbits, it is preferable to start with healthy ones under 6 months of age, and in the case of mice, to start with females or single caged males under 3 months of age.

Amount of Antigen

• The immune system does not respond on a quantitative basis. If the antigen is foreign in nature, a small amount will have the desired effect. Larger amounts of antigen do not give a better response.
• Optimal dose of antigen required to induce a better antibody production.
• A very high and very low doses of antigen may result in unresposiveness.

Adjuvants

• The purpose of adjuvant is to slow the release of antigen into the body, thus maximizing the immune response.
• The best known adjuvant is complete Freund’s Adjuvant (FCA), a suspension of killed mycobacteria (M. tuberculosis, M. Phlei –0.5 mg/ml) in 9 parts of light liquid paraffin with one part of arlacel-A either on weight or volume basis.
• Freund’s incomplete Adjuvant (FIA) is mineral oil without the killed mycobacteria. Currently, FIA alone is used successfully since the mineral oil emulsion gives the required slow release and the Mycobacteria in FCA can divert the immune response.