Flowcytometric analysis of bronchoalveolar lavage fluid cells in polymyositis/dermatomyositis with interstitial pneumonia.

OBJECTIVE: Interstitial lung disease (ILD) is a complication occurring in 10-30% of patients with polymyositis/dermatomyositis (PM/DM) as well as in those with progressive systemic sclerosis (PSS). Clinical features are different between these two disease states, notably with respect to the duration of manifestations, pathological findings, response to steroid therapy etc. However, dissimilarities in pulmonary inflammatory cell characteristics, which, if present at all, would be of critical importance, remain as yet to be clarified.

METHODOLOGY: The phenotypes of lymphocytes and alveolar macrophages in bronchoalveolar lavage fluid (BALF) were analysed to elucidate phenotypic peculiarity of pulmonary inflammatory cells of ILD in PM/DM. Eight PM/DM patients with ILD (mean age 47.9 years) were examined by bronchofibrescopy under local anaesthesia. Bronchoalveolar lavage was performed from the right middle lobe using four 50 mL aliquots of normal saline and the recovered fluid was compared with BALF of ILD in PSS.

RESULTS: Bronchoalveolar lavage fluid cells of PM/DM patients with ILD showed an increased percentage of CD8+ lymphocytes, in particular CD8+ histocompatibility leucocyte antigen-DR positive lymphocytes and CD8+ CD11b-lymphocytes, both of which represent cytotoxic T cells. However, phenotypic differences in these lymphocytes were not found between PM and DM. The percentage of alveolar macrophages with expression of histocompatibility leucocyte antigen-DQ was significantly different among the three groups (PM/DM, PSS, healthy volunteers).

CONCLUSIONS: Cytotoxic T cells may be major pulmonary inflammatory cells of ILD in PM/DM with no apparent difference between PM and DM. In contrast, ILD in PSS was suggested as being likely to be characterized by activated macrophage.