TNF and COVID-19: We also observed that ligand-receptor pairs, including TNF_VSIR, TNF_TNFRSF1B, TNF_TNFRSF1A, and TNF_RIPK1, were weakened in the interaction between CD14+ CD16+ monocyte cells, CD16+ monocyte cells, DCs, and HLA_DR+ Tregs from the severe COVID-19 patients, and the ligand-receptor pair of PF4_CXCR3 was not significantly enhanced in severe COVID-19 patients (Figures 4F–H).