Antibodies or immunoglobulins, as they are sometimes known, are large proteins that circulate in blood. The antibodies are used by the immune system to identify and neutralise foreign bodies such as bacteria, toxins and viruses. Antibodies can react with these foreign bodies and render them harmless, however, the number of antibodies gradually reduces with time so the length of successful immunity can depend on the type of infection. It is, therefore, beneficial to measure the level of immunity.

How do you measure levels of immunity?

When you remove the red and white blood cells and substances such as fibrinogen from blood you are left with serum, with this serum you can determine the antibody titre, this is the highest dilution of serum that reacts to any particular antigen, a highly diluted serum that still reacts to the antigen means there are a high number of antibodies present.

It is important to understand that antibodies are only produced when the body has come into contact with foreign bodies and these weaken over time, therefore if you find a reaction to a high dilution the animal has a strong immune system.

Diagnosing disease with antibody titres

Antibody titres are often used to diagnose infectious disease such as distemper, hepatitis and parvovirus. They are also used to measure whether vaccinations have created an acceptable level of immunity.