Internal Medicine Service: Immune-Mediated Diseases

A strong and healthy immune system is necessary for combating many types of diseases and infections. In healthy dogs and cats, the immune system is tasked with recognizing foreign cells like bacteria or fungi, and then destroying and/or removing them from the body.

There are diseases, however, in which the immune system responds inappropriately, and may begin attacking the animal’s own cells. These conditions, as a group, are called immune-mediated disease.

The Small Animal Internal Medicine service at Purdue University specializes in diagnosing and treating immune-mediated disease in dogs and cats. The Purdue University Veterinary Teaching Hospital has veterinarians in multiple specialties that work together to provide the best care for these conditions.

Immune-mediated diseases in dogs and cats include:

What is an immune-mediated disease?

The most common immune-mediated diseases in animals are those in which the immune system destroys circulating cells like red blood cells or platelets. The body creates inflammation, but instead of directing the inflammation at a pathogen, it directs this inflammation towards the tissues of the body.

Destruction of these vital cells can lead to dangerous anemia, cardiac arrhythmias, and clotting disorders. There are certain infections, toxins, and cancers that can set off the immune system and target these important cells. Therefore, a diagnostic evaluation is necessary for animals with these immune-mediated conditions in order to determine if there is an underlying disease acting as a trigger.

The diagnostic evaluation usually includes routine blood tests, imaging like x-rays or ultrasound, infectious disease testing, and certain specialized blood tests to assess the immune response. If no trigger is found, these diseases are termed idiopathic, and treatment is aimed at suppressing this inappropriate immune response.

What is immune-suppressive therapy?

Immune-suppressive therapy often involves one or more medications designed to reduce and/or eliminate the inappropriate immune response. For the majority of immune-mediated diseases, dogs and cats will remain on some kind of immune-suppressive therapy for 4-6 months. There are some severe cases in which this therapy continues lifelong.

While these immune-suppressive medications are helpful for treating disease, they also pose their own risks. Suppressing the immune system will increase the risk that a dog or cat will get other, simple infections like skin or urinary tract infections.

The Purdue University Small Animal Internal Medicine service works with local veterinarians to monitor these therapies closely to ensure your pet is safe and the proper balance is struck between treating the immune-mediated disease and minimizing the side effects.

Will my pet require a blood transfusion?

Immune-mediated diseases are not limited to the bloodstream. There are diseases of many body systems that can develop an inappropriate immune response.  For the immune-mediated diseases that attack red blood cells, many dogs and cats will require a blood transfusion to help stabilize them. The Purdue University Veterinary Teaching Hospital has a comprehensive blood donor program, in which dogs and cats donate blood to help animals in need.

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