Fig. 3.

The immune response in the SARS-CoV2 positive asymptomatic patients. Asymptomatic patients are SARS-CoV2 infected but do not show the signs of the COVID-19. They produce a higher amount of IL-13, SCF, IL-12, and LIF. IL-13 decreases the ACE2 expression on pulmonary epithelial cells (PECs) and other immune cells therefore a decreased virus entry and replication occurs without the productive infection. SCF increases the apoptosis among CD8⁺ cytotoxic T cells that decrease cytotoxic and pro-inflammatory action against the virus. IL-12 increases the NK cell and T cell antiviral immunity. LIF inhibits the IFN-γ production and induces FoxP3⁺T_regs causing immunosuppression. Hence, a decrease in the virus entry in the cell, generation of the weak pro-inflammatory immune response, and the activation of NK and Th1 cells-mediated anitviral action generate the asymptomatic phenotype in SARS-CoV2 infected people. These asymptomatic patients at their convalescent phase show very low amount of neutralizing IgG Abs.