ANTIPROTEINASE 3 (PR3) ANTIBODIES
ANTIPROTEINASE 3 (PR3), Antiproteinase 3, or antiproteinase 3 antibodies, typically refers to autoantibodies that target proteinase 3 (PR3), which is an enzyme found in the granules of neutrophils, a type of white blood cell. These antibodies are primarily associated with a group of autoimmune diseases known as anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV).
PR3 is an enzyme involved in the immune response and is normally contained within neutrophils, preventing it from causing harm to the body. However, in AAV, the immune system mistakenly produces antibodies that target PR3. This leads to inflammation and damage to small blood vessels, primarily affecting the kidneys, lungs, and upper respiratory tract.
The two main diseases associated with antiproteinase 3 antibodies are:
- Granulomatosis with polyangiitis (GPA), formerly known as Wegener’s granulomatosis: This is a rare and severe form of AAV that primarily affects the upper respiratory tract, lungs, and kidneys.
- Microscopic polyangiitis (MPA): MPA is another type of AAV that mainly affects the kidneys, lungs, and various other organs.
The presence of antiproteinase 3 antibodies is one of the diagnostic criteria for AAV. Detecting these antibodies is typically done through blood tests. Treatment for these diseases often involves immunosuppressive medications to control the autoimmune response and reduce inflammation.
When should I order a PR3 Antibodies Blood Test?
GPA is a rare and serious autoimmune condition that primarily affects the respiratory tract and the kidneys.
Here are some situations in which your healthcare provider may recommend ordering a PR3 antibodies blood test:
- Symptoms suggestive of GPA: If you are experiencing symptoms that could be related to GPA, such as persistent upper respiratory tract infections, sinusitis, lung problems, kidney issues, joint pain, or unexplained fevers, your healthcare provider may order this test to help diagnose or rule out the condition.
- Monitoring an existing GPA diagnosis: If you have already been diagnosed with GPA, your healthcare provider may periodically order PR3 antibodies blood tests to monitor the disease’s activity and response to treatment.
- Evaluation of other autoimmune conditions: In some cases, your healthcare provider may order this test as part of a broader workup to investigate autoimmune disorders. PR3 antibodies can sometimes be elevated in other conditions, so this test can help differentiate between different autoimmune diseases.