Content area
Full Text
Abstract
Rationale: Pulmonary sarcoidosis is classically defined by T-helper (Th) cell type 1 inflammation (e.g., IFN-g production by CD41 effector T cells). Recently, IL-17A-secreting cells have been found in lung lavage, invoking Th17 immunity in sarcoidosis. Studies also identified IL-17A-secreting cells that expressed IFN-g, but their abundance as a percentage of total CD41 cells was either low or undetermined.
Objectives: Based on evidence that Th17 cells can be polarized to Th17.1 cells to produce only IFN-g, our goal was to determine whether Th17.1 cells are a prominent source of IFN-g in sarcoidosis.
Methods: We developed a single-cell approach to define and isolate major Th-cell subsets using combinations of chemokine receptors and fluorescence-activated cell sorting. We subsequently confirmed the accuracy of subset enrichment by measuring cytokine production.
Measurements and Main Results: Discrimination between Th17 and Th17.1 cells revealed very high percentages of Th17.1 cells in lung lavage in sarcoidosis compared with controls in two separate cohorts. No differences in Th17 or Th1 lavage cells were found compared with controls. Lung lavage Th17.1-cell percentages were also higher than Th1-cell percentages, and approximately 60% of Th17.1-enriched cells produced only IFN-g.
Conclusions: Combined use of surface markers and functional assays to study CD41 T cells in sarcoidosis revealed a marked expansion of Th17.1 cells that only produce IFN-g.These results suggest that Th17.1 cells could be misclassified as Th1 cells and may be the predominant producer of IFN-g in pulmonary sarcoidosis, challenging the Th1 paradigm of pathogenesis.
Keywords: lymphocyte; chemokine receptor; inflammation
Sarcoidosis is a granulomatous disease in which the inflammation is thought to be driven in part by activated T-helper (Th) type 1 effector T cells (1-4). The idea that Th1 cells play a key role in sarcoidosis is largely based on experimental observations of increased numbers of CD41 effector T cells, which produce IFN-g,in sarcoidosis bronchoalveolar lavage (BAL) fluid (3, 5-7). After the recent discovery of a new class of Th cells, Th17 cells, several investigators have used a variety of flow cytometry gating strategies to identify IL-17A-producing cells in BAL fluid from patients with sarcoidosis (8-13). Several of these studies also identified IL-17A-secreting cells that expressed IFN-g, but their abundance as a percentage of total CD41 cells was either low or undetermined (9, 11, 12).
Recent...