Increased production off hydrogen peroxide and expression of CD11b/CD18 on alveolar macrophages in patients with active pulmonary tuberculosis

Setting: Alveolar macrophages (AM) are important in host defense against Mycobacterium tuberculosis (TB). β2-integrins, especially CD11a/CD18 and CD11b/CD18, are implicated in leukocyte migration, antigen presentation, phagocytosis, and production of reactive oxygen species Objective: To explore the functional relevance of β2-integrin expression to intracellular H₂O₂ capacity of AM in TB patients. Design: In a prospective study, AM retrieved from 18 active pulmonary TB patients and 18 normal subjects were assessed for β2-integrin expression and intracellular H₂O₂ metabolism capacity by loading with anti-CD11a/CD18, anti-CD11b/CD18 monoclonal antibodies and 2',7' dichlorofluorescein diacetate (DCFH-DA) respectively, and analyzed by flow cytometry. AM from 8 normal subjects were stimulated with tumor necrosis factor-alpha (TNF-α, 10⁵ units/ml) to examine the relationship between H₂O₂ production and CD11b/CD18 expression. Results: The magnitude of DCFH oxidation and CD11b/CD18 expression of AM was higher in TB patients than in normal subjects. The CD11b/CD18 expression was related to the magnitude of DCFH oxidation, but not to lymphocyte numbers or subpopulations (CD4, CD8, CD25). Stimulation of AM with TNF-α increased H₂O₂ production and CD11b/CD18 expression. Pretreatment with CD11b/CD18 monoclonal antibodies inhibited TNF-α-induced H₂O₂. Conclusion: AM in TB patients possessed a higher capacity of oxidant metabolism. The increased CD11b/CD18 expression may be related to the increased respiratory burst response in AM against mycobacterial invasion.