Preferential adsorption of human neutrophil myeloperoxidase isoform III by oral bacteria

Myeloperoxidase isoform activities released by human neutrophils in response to dental and periodontal bacteria

Myeloperoxidase is an enzyme released by polymorphonuclear leukocytes which has been used, experimentally, as an indicator of periodontal disease activity when measured in gingival crevicular fluid. There are three myeloperoxidase isoforms: MPO I, MPO II and MPO III. We examined the activities of myeloperoxidase isoforms released by neutrophils in response to serum-opsonized Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Eikenella corrodens, Capnocytophaga sputigena and Streptococcus sanguis. Isoform activities were determined using intermediate-pressure liquid chromatography and microenzyme assay. A. actinomycetemcomitans stimulated higher levels of myeloperoxidase release than any other oral bacteria unless pre-opsonized with serum (or protein-A-purified immunoglobulin) from an individual with localized juvenile periodontitis. Most oral bacteria stimulated the release of all myeloperoxidase isoforms with a profile enriched in MPO I and diminished in MPO III. Exceptionally, serum-opsonized A. actinomycetemcomitans stimulated myeloperoxidase isoform release in proportion to the neutrophil granule constituency with or without localized juvenile periodontitis serum pre-opsonization. Because myeloperoxidase isoform profiles reflect how neutrophils were stimulated, isoform analysis may refine future diagnostic tests based upon myeloperoxidase.

The neutrophil: mechanisms of controlling periodontal bacteria

The control of potentially periodontopathic microorganisms by host neutrophils is crucial to periodontal health. Neutrophils may use oxidative or nonoxidative mechanisms and either kill bacteria, influence bacterial growth, or modify bacterial colonization in the periodontium. Delivery of antimicrobial substances by neutrophils involves respiratory burst activity, phagocytosis, secretion, or cytolysis/apoptosis. Neutrophils contain a number of antimicrobial components including calprotectin complex, lysozyme, defensins, cofactor-binding proteins, neutral serine proteases, bactericidal/permeability increasing protein, myeloperoxidase, and a NADPH oxidase system. Many of these components are multifunctional and exhibit several mechanisms of antimicrobial activity. When comparisons are made among periodontal bacteria, differences in sensitivity to different components are observed. A hypothesis of specific defense is presented: That specific periodontal diseases can result from the failure of specific aspects of the host immune system (the neutrophil, in particular) in its interaction with specific periodontal pathogens. Failure may be due to phenotypic variation (pleomorphism) within the host or bacterial evasive strategies.