Proteinase 3 (PR3)

Proteinase 3 (PR3) is an enzyme found mainly in certain immune cells called neutrophils. It plays a role in our body's defense system by breaking down proteins during inflammation and fighting infections. PR3 is also involved in various immune responses, and sometimes, it can mistakenly target the body's own tissues, leading to autoimmune conditions like granulomatosis with polyangiitis (formerly Wegener's granulomatosis). In medical tests, antibodies against PR3 can help diagnose such autoimmune diseases. Overall, PR3 is an important component of our immune toolkit, helping control inflammation and infection.