Myeloid-derived suppressor cells in the blood of Iranian COVID-19 patients

Background A cytokine storm and lymphopenia are reported in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection associated with coronavirus disease 2019 (COVID-19). Myeloid-derived suppressive cells (MDSCs) exist in two different forms, granulocyte (G-MDSCs) and monocytic (M-MDSCs) that both suppress T-cell function. Serum IL-6 and IL-8 levels seem to correlate with the number of blood MDSCs. Objective To determine the frequency of MDSCs in severe COVID-19 patients from Iran and their correlations with serum IL-8 levels. Methods 37 severe (8 on ventilation, 29 without ventilation) and 13 moderate COVID-19 patients together with 8 healthy subjects were enrolled at the Masih Daneshvari Hospital, Tehran-Iran between 10th April 2020-9th March 2021. Clinical and biochemical features, serum and whole blood were obtained. CD14, CD15, CD11b and HLA-DR expression on MDSCs was measured by flow cytometry. Results M-MDSCs (P≤0.0001) and G-MDSCs (P≤0.0001) frequency were higher in Iranian COVID-19 patients compared to healthy subjects. M-MDSC frequency was higher in non-ventilated compared to moderate COVID-19 subjects (P=0.004). Serum IL-8 levels were higher in patients with COVID-19 than in normal healthy subjects (P=0.03). IL8 level was significant difference in ventilated, non-ventilated and moderate patients (P=0.005). The frequency of G-MDSCs correlated negatively with INR (r=-0.39, P=0.02). Conclusion Serum IL-8 levels did not correlate with the number of systemic MDSCs in COVID-19 patients. The highest levels of M-MDSCs were seen in the blood of severe non-ventilated patients. MDSC frequency in blood in the current study did not predict the survival and severity of COVID-19 patients.