A decoy oligodeoxynucleotide favors the differentiation of CpG ODN-induced B cells into IL-10-producing Breg-like cells over plasma cells by restoring IRF4/IRF8 imbalance.

The imbalanced expression of interferon regulatory factor (IRF) 4 and IRF8 in activated B cells significantly influences their differentiation and promotes the development of immune-related diseases. Restoring abnormal B cells to appropriate responses may treat these diseases. In this study, an oligodeoxynucleotide (ODN) S2, designed according to the consensus sequence recognized by IRFs in interferon-stimulated response elements, was used as an immunomodulator to investigate its effects on mouse splenic B cells stimulated with the TLR9 agonist CpG ODN, either alone or in combination with antigen, and to explore its underlying mechanisms. The results showed that S2 had a significant negative regulatory effect on CpG ODN induced B cell activation. It also significantly downregulated the production of IL-6 and the percentage of IL-6(+) B cells in splenocytes stimulated by CpG ODN, but significantly upregulated the percentage of IL-10(+) B cells. Interestingly, S2 impaired antibody production both in vitro and in vivo, but rescued mice from lethal inflammatory responses. Further studies showed that S2 could bind IRF4 and IRF8 with high affinity, slightly upregulate phosphorylated IRF4, reduce the expression and nuclear translocation of IRF8, and alter the proportion of IRF4(+), IRF8(+) or double-positive B cells in spleen cells induced by CpG ODN. These results suggest that S2 acts as a decoy directing some B cells to differentiate into IL-10-producing Breg-like cells rather than plasma cells by restoring the TLR9 signal-induced IRF4 and IRF8 ratio imbalance. This indicates its potential as an immunomodulator for the treatment of diseases associated with B-cell abnormalities.