Fig. 3

The immune responses induced by mRNA vaccines. The mRNA vaccines encoding the S protein were inserted into human cells and recognized by antigen-presenting cells (APCs). They elicited robust CD8⁺ and Th1-type CD4⁺ T-cell responses. CD4⁺ Th1 cells promoted CD8⁺ T-cell expansion and differentiation through cytokine (e.g., interleukin [IL]−2) production and expressed interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and IL-2. CD8⁺ T cells also expressed IFN-γ. The circulating T follicular helper (cTfh) cells facilitated B-cell maturation and high-affinity antibody production. The vaccines also elicited robust immune responses and promoted antibody-dependent cellular cytotoxicity (ADCC) activity