Increased bronchoalveolar lavage CD8 lymphocyte subset population in wheezy infants

Episodes of wheezing are very common in infancy but, despite their high prevalence, their mechanism is still poorly understood. To better understand the airway inflammation of wheezing infants, we examined cells of the bronchoalveolar lavage (BAL), focusing on the phenotype of lymphocytes and macrophages by using cytofluorimetry. Twenty-one wheezers (mean age 15.4 months) and seven non-wheezers (mean age 24.1 months) were studied. BAL was collected at fiberoptic bronchoscopy. Total and differential cell counts were similar in both populations. Eosinophils were not detected in the BAL fluid. The cell-surface markers CD2, CD3, CD4, CD7, CD8, CD19, and CD45 were studied for the lymphocyte sub-population analysis. The cell-surface markers CD14, CD54, CD62L, and human leucocyte antigen (HLA)-DR were studied for the macrophage sub-population analysis. A significant increase in the CD8⁺ lymphocyte population (p = 0.03) was observed in wheezers (median 43.1%, 25–75% percentile: 30.1–54.9%), as compared to non-wheezers (median 29.3%, 25–75% percentile: 13.5–34.7%). A significantly (p = 0.04) decreased expression of HLA-DR (mean fluorescence intensity [MFI]) was detected in the macrophage population of the wheezers (median MFI, 7,016; range 2135–7986), as compared to non-wheezers (median MFI, 8,369; range: 6478–8860). The results of the present study suggest that viral infection may have induced a CD8⁺ response in BAL cells.