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Studies of leukotoxin from Actinobacillus actinomycetemcomitans using the promyelocytic HL-60 cell line
Abstract:
The promyelocytic HL-60 cell line was examined for susceptibility to leukotoxin from Actinobacillus actinomycetemcomitans. Strains of A. actinomycetemcomitans which caused lysis of human peripheral blood polymorphonuclear leukocytes also lysed HL-60 cells as determined by release of intracellular lactate dehydrogenase. The killing of HL-60 cells by A. actinomycetemcomitans was dose dependent and temperature dependent, reached maximal levels after 45 min of incubation, and was inhibited by rabbit antisera to A. actinomycetemcomitans. Of 100 oral isolates of A. actinomycetemcomitans from 55 subjects, 16% from 11 healthy subjects, 43% from 13 adult periodontitis patients, 75% from 4 insulin-dependent diabetics, 66% from 2 generalized juvenile periodontitis patients, and 55% from 25 localized juvenile periodontitis patients produced leukotoxin. The same subject could harbor both leukotoxin-producing and -nonproducing isolates. The significantly higher proportion of leukotoxin-producing isolates in the disease groups compared with the healthy group is consistent with the hypothesis that leukotoxin from A. actinomycetemcomitans is an important virulence factor in the pathogenesis of certain forms of periodontal disease.
Insights
Actinobacillus actinomycetemcomitans leukotoxin lyses HL-60 cells and human polymorphonuclear leukocytes. Higher leukotoxin production by oral isolates correlates with periodontal disease, suggesting its role in pathogenesis.
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Actinobacillus actinomycetemcomitans is associated with periodontal disease.
- Leukotoxin is a key virulence factor produced by this bacterium.
- Understanding leukotoxin's effects on immune cells is crucial.
Purpose of the Study:
- To investigate the susceptibility of the HL-60 cell line to Actinobacillus actinomycetemcomitans leukotoxin.
- To determine the prevalence of leukotoxin-producing A. actinomycetemcomitans in various patient groups.
- To assess the role of leukotoxin in the pathogenesis of periodontal disease.
Main Methods:
- Exposure of HL-60 cells to A. actinomycetemcomitans isolates.
- Quantification of cell lysis via lactate dehydrogenase release.
- Dose-response and temperature-dependence studies.
- Inhibition assays using specific antisera.
- Screening of oral isolates from healthy subjects and patients with periodontitis.
Main Results:
- HL-60 cells were lysed by A. actinomycetemcomitans leukotoxin in a dose- and temperature-dependent manner.
- Leukotoxin production was significantly higher in isolates from adult periodontitis, insulin-dependent diabetics, and juvenile periodontitis patients compared to healthy subjects.
- Leukotoxin-producing and non-producing isolates could coexist within the same subject.
Conclusions:
- The HL-60 cell line is a valuable model for studying leukotoxin effects.
- The increased prevalence of leukotoxin-producing A. actinomycetemcomitans in disease groups supports its role as a virulence factor in periodontal disease pathogenesis.