Fig. 1

Effects of mRNA vaccines on immunity. a Effects of exogeneous mRNA on innate immunity. Exogeneous mRNA can be sensed by TLRs in the endosomes as well as receptors like RIG-I and MDA5 in the cytosol. dsRNA can induce a strong IFN1 response. Peptides derived from the translated protein will be processed in the proteasome and presented on MHC-I and MHC-II molecules. b Effects of exogeneous mRNA on innate immunity. APCs can present exogeneous antigens on MHC-II to CD4+ T cells and cross-present on MHC-I to CD8+ T cells. CD4+ T cells provide help to B cells and CD8+ T cells. Finally, clonal expansion of antigen-specific B and T cells results in target cell elimination. c Risk of tumor immune-evasion. Tumors are capable of creating an immunosuppressive micro-environment by recruiting myeloid-derived suppressor cells (MDSCs), regulatory T cells, M2 macrophages and the production of immunosuppressive cytokines. Upregulation of exhaustion markers on T cells, or antigen loss on tumor cells can further drive immune-evasion, exemplarily. CPI might help to regain immunosurveillance. BioRender was used to create the figure