Figure 1.

The schematic representation of immune responses against SARS-CoV-2. a. Optimal innate and adaptive immunity responses: The virus binds to ACE2 to infect cells. The engagement of pattern recognition receptors (PRRs) results in the production of interferons I and other proinflammatory mediators, which induces dendritic cells (DCs) to process antigens and present them to naïve circulating T cells, leading to T cell activation. The activated T cells migrate to the site of infection and secrete effector cytokines, such as IFN-γ. The APCs also induce B cells leading to optimal NAb production. b. Early and sub-optimal NAb activity results in antibody-dependent enhancement, leading macrophages to be exploited for virus replication. This process also causes elevated cytokine production and subsequent immunopathological overreactions

APC: Antigen Presenting Cell, NAb: Neutralizing Antibody