Diagnostic value of TREM-1 and TREM-2 expression in bronchoalveolar lavage fluid in sarcoidosis and other lung diseases

Triggering receptors expressed on myelocytes (TREM) belong to new molecules with a great role in innate immune system and inflammation. While TREM-1 is known for its pro-inflammatory activity, the TREM-2 has anti-inflammatory activity and has a great impact on granuloma formation, typical sign of sarcoidosis and other granulomatous diseases. In our study, we compared the TREM-1 and TREM-2 receptor expressions on the myeloid cell surfaces in bronchoalveolar lavage fluid in patients with pulmonary sarcoidosis (PS), other interstitial lung diseases (ILD), asthma bronchiale (AB), pneumonia, lung cancers, and Quantiferon TB positive patients. We found increased number of all TREM variables (total number, percentage, and mean fluorescence intensity /MFI/) of TREM-1 and TREM-2 positive cells in PS and AB patients compared to the control group of patients with other ILD. In patients with pneumonia, only expression of TREM-1 receptor was increased. In ILD, AB and group of pneumonia patients, the increase of TREM-1 and TREM-2 expression was associated with an increased number of eosinophils. TREM-1 and TREM-2 tests are good diagnostic tests for sarcoidosis. Their sensitivity and specificity are comparable with the currently common using test, that of CD4/CD8 ratio. The combination of both tests (CD4/CD8 ratio test together with TREM-1 and TREM-2 tests) resulted in an increased sensitivity and specificity (Tab. 7, Fig. 1, Ref. 28).