Alveolar Macrophage Subpopulations in Bronchoalveolar Lavage and Induced Sputum of Asthmatic and Control Subjects

Abstract

Background. Alveolar macrophages (AM) are the most numerous immune cells in the airways and are involved in the immunological homeostasis of the lung. Intriguingly, their role in asthma remains unclear probably, in part, because of their heterogeneity. Objective. To characterize AM population from bronchoalveolar lavage (BAL) and induced sputum (IS) of asthmatic and normal subjects using specific biomarkers. Methods. Non-asthmatic non-allergic and allergic mild asthmatic subjects were recruited for this study. AM were obtained from BAL and IS and cytospins were prepared. Immunocytochemistry was performed for nine cellular markers (CD68, RFD7, CD14, CD11b, CD83, CD64, CD80, CD86, and FIZZ1). Results. Asthmatic subjects had more AM RFD7⁺ in BAL compared with IS, whereas control subjects had more AM RFD7⁺ in IS than in BAL. Consequently, there was an increased number of AM RFD7⁺ in BAL of asthmatic subjects compared with BAL of control subjects. AM CD11b⁺ was higher in BAL than in IS in both groups. The expression of FIZZ1, marker of macrophage alternative activation, was similar in asthmatic and normal subjects. Conclusion. The expression of cellular markers on AM differs according to their localization in the lung. Subpopulations of AM may contribute to the inflammatory profile observed in asthmatic subjects.

Keywords:

• alveolar macrophage
• induced sputum
• bronchoalveolar lavage
• immunocytochemistry
• biomarkers