T-lymphocyte activity in HLA-DR17 positive patients with active and clinically recovered sarcoidosis

CD4+ T-lymphocytes are accumulated at the sites of inflammation in sarcoidosis and assumed to play a key role in directing the immune events. By analysing their expression of activation molecules and comparing it between sarcoidosis patients at disease onset and patients at clinical resolution, our aims were to increase the knowledge of their role and find markers of disease activity.

Thirty-two sarcoidosis patients, 23 at disease onset and 9 after clinical resolution, and 36 healthy controls were included. All patients were HLA-DR17 positive, a group sharing several clinical and immunological features. CD4+ T-lymphocytes from bronchoalveolar lavage fluid (BALF) and peripheral blood were analysed for the expression of CD25, HLA-DR and CD69 by flow cytometry.

The CD25 and HLA-DR expression were increased on CD4+ lymphocytes from BALF and peripheral blood at disease onset compared to patients with clinically resolved disease and controls. Interestingly, the percentage of T regulatory (Treg) cells, defined as CD4+ CD25(bright) lymphocytes, was increased in both BALF and blood from patients with active disease. The CD69 expression did not differ between the groups in either compartment.

CD4+ BALF and blood lymphocytes from DR17 positive patients with active sarcoidosis reveal an increased expression of activity markers compared to patients after clinical resolution. An increased number of Treg cells in active sarcoidosis may be involved in the characteristic down-regulation of cell-mediated immune responses in this disease. The results indicate that analysis of these activation markers could be useful as markers of disease activity in sarcoidosis.