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Leukocyte counts and macrophage phenotypes in induced sputum and bronchoalveolar lavage fluid from normal subjects
C Lensmar1, G Elmberger, P Sandgren
1Dept of Medicine, Karolinska Hospital, Stockholm, Sweden.
Insights
Induced sputum (IS) and bronchoalveolar lavage (BAL) yield different leukocyte proportions and macrophage phenotypes. These findings suggest IS and BAL sample distinct lung compartments with unique cellular characteristics.
Area of Science:
- Pulmonary Medicine
- Immunology
- Cell Biology
Background:
- Leukocyte populations in induced sputum (IS) and bronchoalveolar lavage (BAL) are not well-characterized.
- Understanding cellular differences is crucial for accurate lung research and diagnostics.
Purpose of the Study:
- To compare leukocyte counts and macrophage phenotypes between IS and BAL.
- To investigate the effect of dithiothreitol (DTT) on macrophage immunocytochemical staining.
Main Methods:
- Analyzed IS and BAL samples from smokers and nonsmokers.
- Assessed cell viability and counts.
- Characterized macrophages using seven monoclonal antibodies via indirect immunoalkaline phosphatase staining.
Main Results:
- IS samples had lower total cell counts, fewer macrophages, and more neutrophils than BAL samples.
- Macrophage phenotypes differed between IS and BAL, with varying antigen expression in smokers and nonsmokers.
- Dithiothreitol (DTT) did not affect macrophage antigen expression in BAL samples.
Conclusions:
- Induced sputum and bronchoalveolar lavage provide samples from different lung compartments.
- Leukocyte proportions and macrophage phenotypes vary significantly between IS and BAL.
- These differences highlight the distinct cellular environments sampled by each method.
Abstract:
It is unclear whether leukocytes in induced sputum (IS) and bronchoalveolar lavage (BAL) represent the same cell populations. To compare leukocyte counts and macrophage phenotypes and investigate any measurable dithiothreitol (DTT)-mediated effect on macrophage immunocytochemical staining results, IS and BAL samples from nine healthy smokers and seven nonsmokers were examined. BAL and IS samples were processed and cell viability and cell counts were assessed. The macrophages were characterized by seven monoclonal antibodies (RFD1, RFD7, CD11b, CD54, CD68, CD71 and HLA-DR) using an indirect immunoalkaline phosphatase method. Intraindividual comparison of IS and BAL showed that IS samples from smokers and nonsmokers contained a lower total cell count (p<0.01 smokers, p<0.05 nonsmokers), a lower percentage of macrophages (both p<0.05) and a higher percentage of neutrophils (both p<0.05) than BAL samples. In addition, nonsmokers sputum samples contained a lower proportion of lymphocytes (p<0.05) than BAL. The macrophage expression of RFD7 and CD71 was higher in smokers sputum samples (both p<0.05) than in BAL, while nonsmokers sputum macrophages showed a higher expression of CD54 and CD71 (both p<0.05) than BAL macrophages. DTT-incubated BAL samples showed no difference in macrophage antigen expression from BAL samples not exposed to DTT. In conclusion, the relative proportions of leukocytes and the macrophage phenotypes differed between induced sputum and bronchoalveolar lavage suggesting that the methods provide samples from different lung compartments, inhabited by cells with different phenotypes.
