Peripheral blood natural killer cells in sarcoidosis are associated with early cardiac involvement

To evaluate the distribution of circulating immune cell subsets in peripheral blood of patients with sarcoidosis and investigate if there is an association with an underlying cardiac involvement.

Eighty-five newly diagnosed treatment-naïve patients with sarcoidosis (50 women) were included in the study. All patients underwent a thorough cardiac investigation, including cardiac magnetic resonance imaging (CMR). Of all patients, 19 (23.53%) had myocardial involvement, and the NK subpopulation in these patients in peripheral blood was significantly decreased compared to patients without (n = 63, p = 0.001 and p = 0.003 respectively). The absolute number of NKT cells (CD3+CD16/56⁺ ) in patients with cardiac involvement was highly correlated with T2 map increased values in MRI (r = -686, p = 0.041) showing that low NKT cell count correlates with the inflammatory process of the heart. No difference in CD19, CD3, CD4, CD8 and CD3^- NK cell counts was found between groups. Lung severity was not found to correlate with the number of NK cells.

We found that low NK cell count in peripheral blood of patients with sarcoidosis is associated with cardiac involvement, and the number of NK-T cells correlates with CMR findings indicative of myocardial inflammation. This finding might have a potential clinical application in detecting clinically silent cardiac involvement in sarcoidosis and may also suggest potential targets for therapeutic interventions.