In the present study, phagocytosis and the oxidative metabolism of neutrophil granulocytes from five clinically healthy persons with different degrees of
myeloperoxidase deficiency were investigated and compared to those of normal persons. The identification of individuals with
myeloperoxidase deficiency was performed with the Bayer/Technicon H3 blood cell counter, which differentiates the leukocytes by measuring the
peroxidase activity. Neutrophils of three out of five investigated
myeloperoxidase deficient persons showed extremely low
peroxidase indices (-53 and lower), but only the neutrophils of one person totally lacked
myeloperoxidase. This was demonstrated by comparing
myeloperoxidase mass concentration measured with an
enzyme immunoassay, lack of HOCl production, and was further confirmed by measuring
luminol- and
lucigenin-enhanced chemiluminescence. Characteristically,
myeloperoxidase deficient granulocytes showed a strikingly decreased
luminol-enhanced chemiluminescence while the
lucigenin-enhanced chemiluminescence was significantly increased compared to normal granulocytes. Although there is
a DNA sequence homology of about 70%, the activity of
peroxidase in eosinophils was not affected in any
myeloperoxidase deficient person investigated. Moreover, a person with a very rare defect of
eosinophil peroxidase had completely normal
myeloperoxidase activity. The lack of
myeloperoxidase activity is compensated for by an increased phagocytic activity, an increased production of
superoxide anion (
lucigenin-chemiluminescence) and probably by an alternative metabolism of H2O2; since persons lacking
myeloperoxidase activity do not normally suffer from severe
infections, H2O2 is obviously metabolized to other reactive
oxygen substrates than HOCl, e.g. to
OH-radicals.