4-Aminobenzoic acid hydrazide (4-ABAH) is an irreversible inhibitor of myeloperoxidase (MPO, IC50 = 0.3 µM). It reduces the production of hypochlorous acid (HOCl) induced by opsonized zymosan or phorbol 12-myristate 13-acetate (PMA, Cay-10008014) in isolated human neutrophils with IC50 values of 16 and 2.2 µM,...

In normal tissues and in a variety of myeloproliferative disorders, myeloid cells of both neutrophilic and eosinophilic types, at all stages of maturation, exhibit strong cytoplasmic reactivity for MPO. It is readily detected in myeloblasts and immature myeloid cells of acute myelogenous leukemia, progranulocytic...