Decreased percentages of plasmacytoid dendritic cells predict survival in critically ill patients

Critically ill patients admitted to intensive care units (ICUs) experience a broad variety of life-threatening conditions. Irrespective of the initial cause of hospitalization, many experience systemic immune dysregulation. Dendritic cells (DCs) are the most potent antigen-presenting cells and play a pivotal role in regulating the immune response by linking the innate to the adaptive immune system. The aim of this study was to analyze whether DCs or their respective subsets are associated with 30-d mortality in an unselected patient cohort admitted to a medical ICU with a cardiovascular focus. A total of 231 patients were included in this single-center prospective observational study. Blood was drawn at admission and after 72 h. Subsequently, flow cytometry was utilized for the analysis of DCs and their respective subsets. In the total cohort, low percentages of DCs were significantly associated with sepsis, respiratory failure, and septic shock. In particular, a significantly lower percentage of circulating plasmacytoid DCs (pDCs) was found to be a strong and independent predictor of 30-d mortality after adjustment for demographic and clinical variables with an hazard ratio of 4.2 (95% confidence interval: 1.3-13.3, P = 0.015). Additionally, low percentages of pDCs were correlated with additional markers of inflammation and organ dysfunction. In conclusion, we observed low percentages of DCs in patients admitted to an ICU experiencing sepsis, respiratory failure, and cardiogenic shock, suggesting their depletion as a contributing mechanism for the development of immune paralysis. In our cohort, pDCs were identified as the most robust subset to predict 30-d mortality.