Diminished activity of tartrate resistant acid phosphatase in alveolar macrophages from patients with active sarcoidosis.

Alveolar macrophages differ from their percursors in blood, monocytes, by expressing strong activity of the tartrate resistant variant of acid phosphatase (TAcP). A study was carried out to analyse the expression of this enzyme cytochemical marker by alveolar macrophages from bronchoalveolar lavage cells from 34 patients with sarcoidosis and 12 control subjects. Alveolar macrophages from control subjects displayed a strong and homogeneous staining pattern and only 0.1% of cells were negative after staining. Macrophages from patients with sarcoidosis showed reduced TAcP activity and up to 7% of the cells were negative. The percentage of TAcP negative macrophages was correlated with the percentage of lymphocytes and with the ratio of CD4 to CD8 lymphocytes among cells recovered by bronchoalveolar lavage. The reduced TAcP activity in alveolar macrophages from patients with sarcoidosis may be due to an increased recruitment of immature precursors from blood.