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. 2021 Aug 10;6(12):1078–1094. doi: 10.1038/s41578-021-00358-0

Fig. 4. Lipid nanoparticle–mRNA formulations as COVID-19 vaccines.

Fig. 4

After intramuscular injection, lipid nanoparticle–mRNA (LNP–mRNA) vaccines are internalized by somatic cells (for example, muscle cells) and tissue-resident or recruited antigen-presenting cells (APCs)2,4,7,11,17. Moreover, LNP–mRNA vaccines can centre draining lymph nodes, where various immune cells reside, including naive T and B cells2,4,7,11,17. Spike antigens expressed in the cytoplasm are degraded by proteasomes2,4,7,11,17 and major histocompatibility complex (MHC) class I presents the resultant epitopes to CD8+ T cells2,4,7,11,17. Spike antigens can also be endocytosed by APCs. These antigens are degraded in the lysosomes of APCs and presented by MHC II molecules for CD4+ T cells2,4,7,11,17. In addition, secreted spike antigens can be internalized by B cell receptors and processed for presentation to CD4+ T cells by MHC class II molecules2,4,7,11,17. COVID-19, coronavirus disease 2019; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; TCR, T cell receptor.