Myeloperoxidase activity in human gingival crevicular neutrophils

Myeloperoxidase (MPO) activity in neutrophil leucocytes from gingival crevicular exudate and peripheral venous blood was assayed both spectrophotometrically and cytochemically in 50 healthy subjects with and without clinically evident gingival inflammation. All blood neutrophil MPO levels were within the normal range; gingival neutrophil MPO levels were normal in all subjects with inflamed tissue but enzyme activity was not detected in approximately 50 per cent of those with no inflammation. There was positive correlation (p less than 0.0003) between the gingival index and MPO activity. The gingival crevice is an accessible example of a functional site in host defence and it may be that subpopulations of neutrophils are selectively sequestered into such areas in response to chemotactic stimuli.