Bronchoalveolar lavage cell pattern from healthy human lung

Abstract

Bronchoalveolar lavage (BAL) is widely accepted as a key diagnostic procedure in interstitial lung diseases (ILD). We performed a study to obtain reference intervals of differential cell patterns in BAL fluid with special attention to the origin of lavage fluid, e.g. bronchial/alveolar, to atopy and smoking status and to age of the healthy people. We performed bronchoalveolar lavage in 55 healthy subjects with known atopy status (age: 18-64 years, non-smokers/smokers: 34/21) and determined differential cell counts and lymphocyte subsets in BAL fluid and blood. Moreover, in a subgroup of non-smoking healthy individuals we measured the expression of the regulatory T cell marker forkhead box protein 3 (FoxP3) on blood and BAL fluid lymphocytes in addition to a comprehensive set of activation markers. Differential cell counts from the alveolar lavage fraction differed significantly from calculated pooled fractions (n = 11). In contrast, marginal differences were found between atopic and non-atopic subjects. Interestingly, the BAL fluid CD4(+) /CD8(+) ratio correlated strongly with age (r(2) = 0·50, P < 0·0001). We consider the bronchial and alveolar fraction to be lavage fluid from fundamentally different compartments and recommend analysis of the alveolar fraction in diagnostic work-up of ILD. In addition, our data suggest that age corrected BAL fluid CD4(+) /CD8(+) ratios should be used in the clinical evaluation of patients with interstitial lung diseases.

Fig. 1

Representative pictures of cell composition of bronchoalveolar lavage (BAL) fraction I (left) and II (right). L: lymphocyte; M: macrophage; E: eosinophil; Ep: epithelial cell; N: neutrophil.

Fig. 2

Bronchoalveolar lavage (BAL) fluid differential cells counts from pooled fractions (calculated) versus corresponding fractions II in healthy non-smokers (n = 11). The relatively high neutrophil percentages (*) and eosinophil counts (**) are from atopic individuals.

Fig. 3

Scatterplots illustrating strong correlations between age and the percentage of bronchoalveolar lavage (BAL) fluid CD4⁺ lymphocytes, CD8⁺ lymphocytes, the CD4^+/CD8⁺ ratio and the CD103⁺CD4⁺/CD4⁺ ratio in healthy non-smokers.

Fig. 4

Forkhead box protein 3 (FoxP3) median fluorescence intensity on CD4⁺ cells [median fluorescence intensity of the positive fraction (MFI)] (a) and the proportion of FoxP3⁺ positive CD4⁺ cells (b) were significantly higher in BAL fluid than in peripheral blood samples.