Granulocytes and their secretory products, myeloperoxidase and eosinophil cationic protein, in bronchoalveolar lavage fluids from two lung lobes in normal subjects

The interlobar variability of lavage neutrophils and eosinophils was studied in twelve healthy subjects. In addition, the interlobar variation of the neutrophil cell marker myeloperoxidase (MPO) and the eosinophil cell marker eosinophil cationic protein (ECP) was assessed. Bronchial washes (BW), as defined by the first aspirated lavage aliquot, and bronchoalveolar lavage (BAL) fluids were compared. One subsegment of the right middle lobe and one subsegment of the right lower lobe were lavaged in the same session. Interlobar consistency of neutrophil and eosinophil cell recoveries was observed but, in contrast, the levels of MPO or ECP did not correlate in lavage fluids aspirated from the two lobes. These results suggest that BAL cell content from a single lobe of the lung in healthy subjects does reflect the cell populations throughout the airways, while the levels of soluble proteins may differ between the lobes. Such a variation questions the correlation between cells and their secretory products or the correlation between levels of solutes in lavage fluid and in the underlying tissue. Further methodological studies appear warranted to elucidate whether cell and solute recoveries accurately reflect the underlying pathology.