Determining T-cell phenotypes of lung cells obtained by bronchoalveolar lavage (BAL) is frequently clinically useful, particularly for evaluating causes of interstitial lung disease. The current standard of determining CD4/CD8 T-cell subsets by immunohistochemical (IHC) staining of cytocentrifuge slides is labor-intensive and subject to interpreter variation. Flow cytometry (FCM) is a precise and rapid method commonly used in research to characterize cells in the lung. However, few studies address the methodology of analysis of BAL lymphocytes by FCM.
Patients underwent bronchoscopy for clinical purposes. A BAL cell differential and T-cell subtype was requested by the treating physician to supplement the evaluation of patients with suspected interstitial lung disease. We used a commercially available T-cell antibody reagent, approved for analysis of blood via FCM, for T-cell subtyping of clinical BAL specimens.
The percentages of CD4 and CD8 T-cell populations, as well as the CD4/CD8 ratios showed excellent correlation with IHC staining of cytocentrifuge slides regardless of the acquisition program used, as long as the gating strategy remained consistent (r > or = 0.9693 for CD4, r > or = 0.9589 for CD8, and r > or = 0.9485 for the CD4/CD8 ratio).
These findings validate the use of standardized, commercially available antibody cocktails for BAL lymphocyte subtyping, making this technique available to clinicians and researchers with access to a three-color or four-color flow cytometer.