Abstract
Background Sarcoidosis and hypersensitivity pneumonitis (HP) are immunologically mediated processes caused by hypersensitivity reaction accompanied by similar features including lymphocytic alveolitis and granuloma formation. Recent studies describe the role of TREM receptors in T cell activation, differentiation, and granuloma formation. Alveolar macrophages activation via TREM receptors may be the key factor mediating subsequent immune response. The aim of the study was to analyse TREM-1 and TREM-2 expression to identify further molecular mechanisms participating in the immunopathogenesis of sarcoidosis and HP. Methods Flow cytometry was performed to analyse TREM-1 and TREM-2 expression on CD14+ cells in bronchoalveolar lavage fluid from patients having sarcoidosis or HP and a control group. Results The study proved increased TREM-1 expression on alveolar macrophages in pulmonary sarcoidosis and diminished TREM-1 expression in HP-Sarcoidosis: median: 76.7; HP: median: 29.9; control: median: 53.3, (sarcoidosis versus HP: p < 0.001; sarcoidosis versus control: p < 0.05). TREM-2 expression was increased in both, sarcoidosis and HP-sarcoidosis: median: 34.79; HP: median: 36.00; control: median: 12.98, (sarcoidosis versus control: p < 0.05; HP versus control: p < 0.05). Correlation analysis showed negative correlation between TREM-1 and total number of CD8+ cytotoxic T cells. In sarcoidosis TREM-1 expression decreased with changes of HRCT image, decrease in CD4/CD8 ratio and decrease in DLCO. Conclusions Differences in TREM receptor expression in sarcoidosis (increase in TREM-1 and TREM-2) and HP (increase in TREM-2) and correlation analysis suggests that activation via TREM may participate in typical immunological characteristics of sarcoidosis and HP.
Highlights
Sarcoidosis and hypersensitivity pneumonitis (HP) are classified within diffuse parenchymal lung diseases [1]
In patients with pulmonary sarcoidosis we detected an increased percentage of Triggering receptors expressed on myeloid cells (TREM)-1+ CD14+ cells and mean fluorescence intensity (MFI) compared with HP patients and control group (CG) subjects in Bronchoalveolar lavage fluid (BALF): percentage (Figure 1(a))—sarcoidosis: median: 76.7, interquartile range (IQR): 21.2; HP: median: 29.9, IQR: 43.6; CG: median: 53.3, IQR: 35.89
TREM-2 expression on CD14+ cells from BALF was increased in pulmonary sarcoidosis and HP patients compared with CG subjects in both presented variables: percentage of TREM-2+
Summary
Sarcoidosis and hypersensitivity pneumonitis (HP) are classified within diffuse parenchymal lung diseases [1]. Total number of cells and percentage of lymphocytes in BALF. Normal or mildly elevated total cell count with lymphocytosis (usually 20 × 106/100 mL BALF) with remarkable increment of lymphocytes (usually >50%). Sarcoidosis and hypersensitivity pneumonitis (HP) are immunologically mediated processes caused by hypersensitivity reaction accompanied by similar features including lymphocytic alveolitis and granuloma formation. Recent studies describe the role of TREM receptors in T cell activation, differentiation, and granuloma formation. Alveolar macrophages activation via TREM receptors may be the key factor mediating subsequent immune response. The aim of the study was to analyse TREM-1 and TREM-2 expression to identify further molecular mechanisms participating in the immunopathogenesis of sarcoidosis and HP. Correlation analysis showed negative correlation between TREM-1 and total number of CD8+ cytotoxic T cells. Differences in TREM receptor expression in sarcoidosis (increase in TREM-1 and TREM-2) and HP (increase in TREM-2) and correlation analysis suggests that activation via TREM may participate in typical immunological characteristics of sarcoidosis and HP
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