Fig. 1

Mechanisms in adverse and protective immune response for SARS-CoV-2. Upper panel (red). Adverse immune response in the presence of SARS-CoV-2 include mechanisms like complement hyperactivation and hypercoagulable state, excessive macrophage migration, macrophage activation syndrome, NK exhaustion, insufficient antigen presentation, exhausted CD4⁺ and CD8⁺ T cell and antibody-dependent enhancement (ADE) *This response has been described by in vitro models. Lower panel (blue). Protective immune response is characterized by complement system activation trough IgM natural antibodies (** this has been suggested as an initial barrier for SARS-CoV-2 infection), TLRs activation, NK and T cell normal activation and antibody virus neutralization by B cells. APC antigen presenting cell, ER endoplasmic reticulum, FcgRII receptor II for the Fc region of immunoglobulin G, GM-CSF Granulocyte–macrophage colony-stimulating factor, MAC membrane attack complex, MBL mannan-binding lectin, MHC major histocompatibility complex, MSP mannose-associated serine proteases, Nab neutralizing antibody, TCR T-cell receptor, TLR Toll-like receptor