Figure 2.

Diagram of the theory of functioning of anti-COVID-19 mRNA vaccines. A1–2 The simplistic theory representing the production and presentation of Spike protein by APCs to lymphocytes; A1: production of Spike by local muscle cells and release (by shedding) of soluble S that would be captured and processed by APC for immune stimulation; A2: the LNPs transfect the mRNA into APCs, which then produce and present in the context of MHC Spike to immune cells. B. Theoretical consequences of the expression of Spike protein by cell types other than immune cells transfected by mRNA containing LNP. B1: S protein released by somatic cells stimulates the immune system via APC; B2: interaction of blood platelets with S protein on the membrane of endothelial cells; B3: specific antibodies bind to S protein on the membrane of somatic cells (myocardium, endothelium, etc.) and activate the Complement system (or antibody-dependent cytotoxicity; not shown) leading to cell death; B4: specific CD8+ T lymphocytes (T8) attack endothelial cells expressing S protein. Abbreviations and symbols: LNP: lipid nanoparticle; APC: antigen-presenting cell; MHC: Major Histocompatibility Complex; S: Spike; T and B: lymphocytes; V: Virus; E: Endothelial cell; AB: Antibody; ADCC: Antibody-dependent cell cytotoxicity; ACE2: angiotensin-converting enzyme 2. Solid line arrows: action, operation; dashed line arrows: moving, displacement.