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Airway interleukin-8 in elderly patients with bacterial lower respiratory tract infections
P Ponglertnapagorn1, K Oishi, A Iwagaki
1Department of Internal Medicine, Nagasaki University, Japan.
Abstract:
We investigated the interleukin-8 (IL-8) levels and neutrophil numbers in the sputum of 9 elderly patients with lower respiratory tract infections, including Pseudomonas aeruginosa infection, before and after treatment with various antimicrobial agents. The IL-8 levels in sputum supernatants and the neutrophil numbers in sputum smears from 9 patients decreased significantly after the elimination of the causative respiratory pathogens. We also demonstrated that human recombinant IL-8 at a range of 6.25-25 ng/ml significantly enhanced opsonophagocytic killing of P. aeruginosa immunotype-1 strain by human neutrophils in the presence of a serotype-specific anti-lipopolysaccharide monoclonal antibody and fresh normal human serum. These data suggest that the level of IL-8 production in the airways of patients with lower respiratory tract infections is dependent on bacterial densities, and indicate the important role of IL-8 not only in neutrophil migration but also in opsonophagocytic killing of bacteria in the lower respiratory tract.
Insights
Interleukin-8 (IL-8) levels and neutrophil counts in elderly patients with lower respiratory tract infections decreased post-treatment. IL-8 also enhanced bacterial killing by neutrophils, suggesting a dual role in infection response.
Area of Science:
- Immunology
- Microbiology
- Gerontology
Background:
- Lower respiratory tract infections (LRTI) pose significant health risks, particularly in elderly populations.
- Neutrophils and cytokines like interleukin-8 (IL-8) are key components of the innate immune response to bacterial pathogens.
Purpose of the Study:
- To investigate the relationship between interleukin-8 (IL-8) levels, neutrophil counts, and bacterial load in elderly patients with LRTI.
- To determine the role of IL-8 in neutrophil-mediated opsonophagocytic killing of Pseudomonas aeruginosa.
Main Methods:
- Sputum samples from 9 elderly patients with LRTI were analyzed for IL-8 levels and neutrophil counts before and after antimicrobial treatment.
- In vitro experiments assessed the effect of human recombinant IL-8 on the opsonophagocytic killing of P. aeruginosa by human neutrophils.
Main Results:
- A significant decrease in sputum IL-8 levels and neutrophil numbers was observed after successful pathogen elimination.
- Human recombinant IL-8 demonstrated a dose-dependent enhancement of P. aeruginosa opsonophagocytic killing by neutrophils.
Conclusions:
- Airway IL-8 production in LRTI patients correlates with bacterial burden.
- IL-8 plays a crucial role in both neutrophil recruitment and enhancing bacterial clearance in the lower respiratory tract.