Background/Purpose: In patients with systemic sclerosis (SSc), plasmacytoid dendritic cells (pDCs) increase in the bronchoalveolar lavage (BAL) and lung tissues (Kafaja S, et al, JCI Insight 2018). Importantly, the frequency of pDCs in the lungs of patients with SSc correlated with the severity of interstitial lung disease, and with the frequency of CD4⁺ and IL-4⁺ T-cells in the lung. A pivotal role of pDCs was shown in animal studies, where the depletion of pDCs ameliorated fibrosis in the bleomycin model. These data suggest a role of pDCs in the pathogenesis of fibrosis. Fibroblast proliferation and accumulation around pulmonary vessels is also an early and important event during the development of pulmonary arterial hypertension (PAH). Here, we explore a possible relationship between pDCs and pulmonary hypertension.

Methods: Previous studies have suggested the utility of HRCT-determined pulmonary artery diameters in predicting pulmonary hypertension. In one study, right pulmonary artery diameter of more than 18.7±2.8 mm was considered abnormal, and main pulmonary artery diameter of >29 mm was predictive of pulmonary hypertension. Hence, to begin to investigate a relation between immune cell subsets and subclinical pulmonary arterial hypertension, we analyzed correlation between diameters (mm) of main or right pulmonary arteries and frequencies (% of total) of cell types in BAL. Frequencies of cellular subsets from RML and RLL were averaged. Next, we stained lung tissue slides from patients with SSc-PAH using markers for pDCs and blood vessels (alpha-smooth muscle cells and endothelial cells).

Results: The frequencies of pDCs correlated with the diameters of both main (r = 0.45) and right pulmonary arteries (r = 0.57). There was no correlation between the frequencies of T-cells (CD4⁺, CD8⁺, Th2 and Tc2) and pulmonary artery diameters. We further found increased pDCs around blood vessels and other areas of lungs from patients with SSc-PAH as compared to control lungs.

Conclusion: These data argue for a possible role of pDCs in SSc-associated pulmonary vascular disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/plasmacytoid-dendritic-cells-in-bronchoalveolar-lavage-correlate-with-pulmonary-artery-diameter-and-infiltrate-perivascular-areas-in-the-lungs-from-patients-with-systemic-sclerosis-associated-pulmonar/