Bronchoalveolar lavage fluid eosinophils are correlated to natural killer cells in eosinophilic pneumonias.

BACKGROUND

Eosinophilic lung diseases comprise a group of heterogeneous pulmonary disorders linked by increased eosinophils in bronchoalveolar lavage fluid (BALF). There is supporting evidence that natural killer (NK) cells participate in the regulation of eosinophilic inflammation.

OBJECTIVE

Our aim was to investigate the relationship between eosinophils and NK cells in BALF in patients with different interstitial lung diseases (ILDs) focusing on eosinophilic pneumonias.

METHODS

Of 114 patients who presented with increased BALF eosinophils (>5%), 74 patients were classified into the following groups: 27 had eosinophilic pneumonia (EP), 17 had idiopathic pulmonary fibrosis (IPF), 16 had hypersensitivity pneumonitis (HSP) and 14 had cryptogenic organizing pneumonia (COP/BOOP). Total BALF cells, cell density and cell differential counts were assessed and lymphocyte subsets CD3+, CD4+, CD8+, CD19+, CD3-CD16/56+ (NK) and CD3+CD16/56+ (NKT) were determined by flow cytometry.

RESULTS

Significant differences were observed in the percentages of lymphocytes (p < 0.001) and CD3+CD16/56+ cells (p = 0.023) among patient groups. In patients with EP, the percentage of eosinophils correlated positively with the number of CD3-CD16/56+ cells (r = 0.522, p = 0.005), the percentage of CD3-CD16/56+ cells (r = 0.690, p < 0.001), and the absolute count of CD3+CD16/56+ absolute cells (r = 0.609, p = 0.001). However, in patients with IPF, HSP or COP/BOOP, no correlation between the percentage of eosinophils and CD3-CD16/56+ or CD3+CD16/56+ cells was observed.

CONCLUSIONS

Eosinophil inflammation seems to develop through a different pathway in EP compared to other ILDs.