ODN 1826 is a class B CpG oligodeoxynucleotide adjuvant with phosphorothioate modifications and specific CpG motifs. It stimulates robust B cell proliferation and antibody secretion by activating the TLR9 receptor. ODN 1826 also induces plasmacytoid dendritic cells (pDCs) to release proinflammatory cytokines like IL-6 and IL-12. Notably, its linear structure without palindromic sequences enhances the Th1 immune response. Extensively used in murine vaccine models, especially for anti-tumor and anti-infection studies, ODN 1826 significantly boosts antigen-specific antibody titers and CD8+ T cell activity, making it a key tool for TLR9-dependent immune activation.