Figure 1.

Mechanism of immune activation by mRNA-LNPs vaccines: Upon administration, mRNA-LNPs are internalized by immune cells, where the mRNA is released from the LNPs. The mRNA is then recognized by ribosomes, leading to the translation of antigenic proteins. These proteins are processed and degraded by proteasomes producing small peptides that then get loaded on major histocompatibility complex class I (MHC I) molecules and presented on the cell surface, which binds to the T cell receptor (TCR), activating CD8+ T cells to kill infected cells. The produced antigen can also be endocytosed by antigen-presenting cells (APCs) and further degraded by the lysosomes producing small peptides that then get loaded on major histocompatibility complex class II (MHC II) molecules for recognition by CD4+ T cells, which subsequently activate both the cellular immune responses by secreting inflammatory cytokines and the humoral immune responses by activating B cells.