Pulmonary and blood dendritic cells from sarcoidosis patients more potently induce IFNγ-producing Th1 cells compared with monocytes

Sarcoidosis is a systemic inflammatory disease mainly affecting the lungs. The hallmark of sarcoidosis are granulomas that are surrounded by activated T cells, likely targeting the disease-inducing antigen. IFNγ-producing Th1 and Th17.1 T cells are elevated in sarcoidosis and associate with disease progression. Monocytes and dendritic cells (DCs) are antigen-presenting cells (APCs) and required for T cell activation. Several subsets of monocytes and DCs with different functions were identified in sarcoidosis. However, to what extent different monocyte and DC subsets can support activation and skewing of T cells in sarcoidosis is still unclear. In this study, we performed a transcriptional and functional side-by-side comparison of sorted monocytes and DCs from matched blood and bronchoalveolar lavage (BAL) fluid of sarcoidosis patients. Transcriptomic analysis of all subsets showed upregulation of genes related to T cell activation and antigen presentation in DCs compared with monocytes. Allogeneic T cell proliferation was higher after coculture with monocytes and DCs from blood compared with BAL and DCs induced more T cell proliferation compared with monocytes. After coculture, proliferating T cells showed high expression of the transcription factor Tbet and IFNγ production. We also identified Tbet and RORγt coexpressing T cells that mainly produced IFNγ. Our data show that DCs rather than monocytes from sarcoidosis patients have the ability to activate and polarize T cells towards Th1 and Th17.1 cells. This study provides a useful in vitro tool to better understand the contribution of monocytes and DCs to T cell activation and immunopathology in sarcoidosis.