Association between M1 and M2 macrophages in bronchoalveolar lavage fluid and tobacco smoking in patients with sarcoidosis

INTRODUCTION Sarcoidosis is a granulomatous disease, which most often affects the lungs. The role of alveolar macrophages (AMs) in granuloma formation in sarcoidosis has been established. Recently, 2 macrophage populations have been described: M1 and M2. In our styudy, we focused on the effect of tobacco smoking on sarcoidosis. The number of AMs in the lungs of smokers is significantly increased; therefore, it is interesting to study the effect of smoking on AM polarization in sarcoidosis. 

OBJECTIVES The aim of the present study was to identify M1 and M2 macrophages in bronchoalveolar lavage (BAL) fluid from patients with sarcoidosis and assess the effect of smoking on these cells. 

PATIENTS AND METHODS The study included 36 patients with confirmed sarcoidosis (18 smokers and 18 nonsmokers). Macrophage populations in BAL fluid were assessed by immunocytochemistry using anti-CD40 and anti-CD163 antibodies (for M1 and M2, respectively). The BAL fluid concentration of interleukin 10 (IL-10) was measured using an enzyme-linked immunosorbent assay. 

RESULTS We identified 3 populations of macrophages stained with anti-CD40 and anti-CD163 antibodies: small strongly positive cells, large weakly positive cells, and negative cells. The median proportions of these macrophages were 61%, 35%, and 2%, respectively, for CD40, and 55.5%, 35%, and 5%, respectively, for CD163; the proportions did not differ significantly between smokers and nonsmokers. Only the proportion of CD163-negative cells was significantly lower in smokers compared with nonsmokers (3.3% vs. 9.5%, P <0.05). The IL-10 concentration in BAL fluid was below the detection limit. 

CONCLUSIONS We did not observe any association between tobacco smoking and macrophage polarization in patients with sarcoidosis. However, our study revealed 2 populations of CD40- and CD163-positive cells, which may indicate that macrophages are involved in granuloma formation and provide direction for future research.