Usefulness of non-specific esterase stain for the morphometric evaluation of alveolar macrophage heterogeneity in human lung diseases

Alveolar macrophage (AM phi) heterogeneity has been used as a parameter of AM phi involvement in animal models of disease. However, scarce and contradictory results have been reported in humans. In order to evaluate whether the use of non-specific esterase stain (Alpha-naphthyl-esterase: ANAE), a histochemical reaction characteristic of mononuclear phagocytes, could improve the study of bronchoalveolar cells (BAC) in humans, differential counts in slides of BAC stained with ANAE or conventional May-Grunvald Giemsa (MGG) were compared, and cell diameters were measured in ANAE-stained slides. No differences were observed between differential counts obtained with the two stains. However, when the distribution of cell diameters was investigated, ANAE provided better differentiation between small AM phi and large lymphocytes and better definition of cell limits of AM phi. Furthermore, an increase of AM phi heterogeneity was observed in patients with interstitial pulmonary diseases, due to an increase of large AM phi. Thus ANAE stain can improve the morphometric study of BAC and could be useful in the study of AM phi in human diseases.