COVID-19 severity associates with pulmonary redistribution of CD1c+ DC and inflammatory transitional and nonclassical monocytes

SARS-CoV-2 is responsible for development of COVID-19 in infected individuals, who can either exhibit mild symptoms or progress towards a life-threatening acute respiratory distress syndrome (ARDS) Exacerbated inflammation and dysregulated immune responses involving T and myeloid cells occur in COVID-19 patients with severe clinical progression However, the differential contribution of specific subsets of dendritic cells and monocytes to ARDS is still poorly understood In addition, the role of CD8+ T cells present in the lung of COVID-19 patients and relevant for viral control has not been characterized Here, we have studied the frequencies and activation profiles of dendritic cells and monocytes present in the blood and lung of COVID-19 patients with different clinical severity in comparison with healthy individuals Furthermore, these subpopulations and their association with antiviral effector CD8+ T cell subsets were also characterized in lung infiltrates from critical COVID-19 patients Our results indicate that inflammatory transitional and non-classical monocytes and CD1c+ conventional dendritic cells preferentially migrate from blood to lungs in patients with severe COVID-19 Thus, this study increases the knowledge on specific myeloid subsets involved in the pathogenesis of COVID-19 disease and could be useful for the design of therapeutic strategies to fight SARS-CoV-2 infection