Evaluation of Dendritic Cell Subpopulations Frequency in COVID-19 Patients and their Correlation with Disease Severity.

Background: COVID-19 (2019) clearly demonstrates an imbalanced immune response. Variations in the function and subtypes of dendritic cells (DCs) may have effects on immune responses in COVID-19 patients and contribute to immunopathology. Objective: To assess the phenotype and frequency of Plasmacytoid dendritic cells (pDCs), Conventional DCs (cDCs), and double-positive DCs in COVID-19 patients admitted to the ICU and non-ICU compared to the healthy control group. Methods: The study included 10 healthy individuals and 25 COVID-19 patients. In the second week of their illness, Peripheral blood mononuclear cells (PBMCs) were isolated from the patients and labeled with targeted antibodies for HLA-DR, CD123, and CD11c. The samples were then analyzed using flow cytometry. The COVID-19 patients were divided into two ICU and non-ICU groups and were closely monitored throughout the study. Results: In comparison to healthy controls, COVID-19 patients exhibited a significantly lower pDCs ratio (P=0.04). Patients were categorized into two groups: (A) the ICU group (n=11; 44%) and (B) the non-ICU group (n=14; 56%). The frequency of pDC was significantly lower in ICU patients than in non-ICU patients (P<0.01). Although not statistically significant, ICU patients had a lower frequency of cDCs and double positive DCs compared to non-ICU patients. Additionally, a significant association between the age of COVID-19 patients and cDC levels was observed (p=0.049). Conclusion: SARS-CoV-2 can evade attacks from the immune response by reducing the number of DCs and suppressing their function of DCs, ultimately resulting in weakened development of both innate and adaptive immunity.