Fig. 2

Immune responses induced by cancer vaccines. (1) Upon vaccination, antigen-presenting cells (APCs), particularly dendritic cells (DCs), capture, process, and present antigens on their surface. Different DC subsets possess distinct abilities to activate specific T cell subsets. As DCs mature, they migrate to secondary lymphoid organs like draining lymph nodes. (2) For effective T cell activation, three critical signals are required. Signal 1 is the combination between antigen-MHC complexes on the APC and T cell receptors. Signal 2 involves co-stimulatory molecules, which amplify the activation signal. Signal 3 consists of immunomodulatory cytokines and chemokines that influence T cell differentiation and functions. Once activated, T cells differentiate into effector cells, including CD4⁺ helper T (Th) cells, cytotoxic CD8⁺ T lymphocytes (CTLs), and memory T cells. CD4⁺ T cells, along with follicular dendritic cells (fDCs), assist in the B cells maturation, leading to the differentiation into antibody-producing plasma cells and memory B cells. (3) Activated immune cells infiltrate the tumor and exert anti-tumor functions. CTLs induce tumor cell apoptosis through perforin, granzymes, and Fas ligand engagement, while B cells employ antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). Tumor-infiltrating APCs can also present antigens to boost cellular immune responses against tumor. cDCs, conventional DCs; pDCs, plasmacytoid DCs; Mo-DCs, monocyte-derived DCs; CCR, C–C motif chemokine receptor; IFN, interferon; IL, interleukin; TNF, tumor necrosis factor; CD40L, CD40 ligand; PD-1, programmed death-1; PD-L1, programmed death ligand-1