Fig. 8.

Possible immune reactions induced by the SARS-CoV-2. The predictions are based on studies of SARS-CoV and MERS-CoV viruses. Non-specific recognition by innate immune receptors (e.g., RNA sensors, TLR7/8, RIG-I/MDA-5, and NLRP3 inflammasome) seems to be the first effect of the virus within alveolar epithelial cells. The main transcription factors involved in the induction of inflammatory mediators (e.g., IL-1β, IL-6, and type I IFNs) are NF-κB and IRF3/7. The antiviral activity of type I IFNs is augmented by many ISGs such as RNAse L. Cell-based immunity is based on macrophages, B cells, and T cells, which directly eliminate viral particles. However, hyper-inflammation resulting from an unbalanced action of the immune system could exacerbate COVID-19 outcomes.