Immunity is a term that describes a state of having sufficient biological defenses to avoid infection, disease or other unwanted biological invasion such as cancer. This defense is principally made up white blood cells and small protein cell-signaling molecules called cytokines. Thus the treatment of cancer or other disease by inducing, enhancing or suppressing an immune response is called immunotherapy. This broad term includes the use of immunomodulators, which are naturally derived and synthetic preparations such as vaccines and medications that can be used for the treatment of cancer.

Most immunotherapies are designed to stimulate the immune system. However, the alternate approach of suppressing the immune system can also be used. An example of when immune suppression might be indicated is when trying to overcome the body's immune tolerance of cancer; a condition where tumor cells inhibit the natural immune system defenses in order to survive.

Although extensive research in this complex area of cancer treatment is being conducted, many studies are still ongoing and only few agents have proven to be safe and beneficial. Recently great attention has been placed on vaccines which are defined as a biologic preparation that contains a weakened agent of the disease (bacteria, virus, tumor cell) or constituent of it (DNA, RNA, protein) given to improve immunity. An example of such therapy for the treatment of cancer in animals is the DNA-based canine melanoma vaccine used to mitigate the high risk of tumor metastasis.

One well known immunomodulator in human oncology is Rituximab. Rituximab is an antibody therapy used in the treatment of non-Hodgkin's lymphoma. Although animals develop cancers similar to humans, they are not identical. For this reason, agents such as Rituximab are not beneficial across species.

Whenever possible, adjunctive therapies such as vaccines or immunotherapy will be used. Your veterinary oncologist will discuss with you if immunotherapy may be a benefit for your pet.