Answer:
So... MPO is most abundantly expressed in neutrophil granulocytes, and produces hypohalous acids to carry out their antimicrobial activity through oxidative damage during the respiratory burst. It requires heme as a cofactor.
Regarding environmental factors ... obviously the first factor is the presence of an infection and inflammation that cause an increase in the activity and production of MPO. Second, alterations in the MPO gene cause its congenital deficiency which predispose to infections.
Rheumatoid arthritis is an autoimmune and autoinflammatory rheumatoid disease in which significant joint damage is observed. In the joint capsule, inflamed infiltrates are observed composed of neutrophils and lymphocytes. Measurement of MPO levels in the joint cavity could therefore be related to the amount of neutrophils and thus to the extent of the inflammatory damage.
