Table 1 The main cells involved in innate immunity and their biological functions in COVID-19 patients
Cell types | Major functions | Cell Responses in SARS-COV-2 infection | Severe cases VS mild | Cytokine release | References |
|---|---|---|---|---|---|
Neutrophils | Kill pathogens in three main ways: phagocytosis, degranulation, and form neutrophil extracellular traps (NETs) | Increased level of NETs, which are related to ARDS | Contain immature neutrophils in severe patients Increased CD63+, CD274+ neutrophils in severe infected patients | IL-1β, IL-6, and CXCL8 | Papayannopoulos [105] Middleton et al. [109] Schulte-Schrepping et al. [116] Neeland et al. [117] Vanderbeke et al. [113] |
Macrophages | Resolve inflammation, repair damaged tissues, and trigger phagocytosis | High level of pro-inflammatory macrophages in BALF from COVID-19 patients | Higher level of cytokines and chemokines in lung macrophages from severe patients | IL-1ß, IL-6, IL-10, TNF-α, IFN-α/β, CCL-2, CCL-3, CCL-4 and CXCL10 | Liao et al. [95] Zheng et al. [122] |
NK cells | Use apoptosis to eliminate pathogen-infected cells and produce cytokines | Reduced NK cell levels | Significant reduction in NK cells in severe patients Upregulated NK cells expression of IFN-α related genes | Il-6, INF-γ and TNF-α/β | Bao et al. [126] Zheng et al. [132] Krämer et al. [133] Market et al. [125] |