MPO and arteritis: To investigate whether the trimodal pattern of MPO expression observed in the very early phases of STEMI was also present in other systemic inflammatory syndromes, we studied conditions of leukocyte activation associated with microbial infection (sepsis) or with self-sustained systemic inflammation (rheumatoid arthritis, ANCA-associated small-vessel vasculitis, polymyalgia rheumatica and giant cell arteritis) (Tables 2 and 3).