PDC and COVID-19: Interleukin (IL)-6 concentrations were significantly increased in COVID-19 patients (p < 0.0001 vs. controls), and negatively correlated with the absolute counts of circulating CD1c+ cDC2 (r = −0.29, p = 0.034) and CD303+ pDC (r = −0.29, p = 0.036) subsets.