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. 2023 Oct 16;11(10):1600. doi: 10.3390/vaccines11101600

Figure 5.

Figure 5

Schematic representation of the mRNA mechanism of action in promoting the adaptive immune response. mRNA is first internalized into the antigen-presenting cell (1) and an endosome containing the mRNA is formed (2). mRNA must exit the endosome into the cytoplasm to avoid degradation in the phagolysosome (3). Once in the cytoplasm, the mRNA is translated by ribosomes (4). Part of the synthesized antigen is transported to the surface of the antigen-presenting cell (5), where it can be recognized by B-lymphocytes (6), which end up forming clones of plasma cells synthesizing antibodies against the antigen (7). Another portion of the synthesized antigen can be secreted into the intercellular space (8), where it can be captured (9) and degraded as part of the phagolysosome (10) of another antigen-presenting cell. After degradation, the antigen is presented as part of the MHC class II (11). The third pathway of the synthesized antigen is proteasomal degradation into peptides within the synthesizing cell (12). The peptides are then presented as part of the MHC class I (13).