CpG-DNA stimulates cellular and humoral immunity and promotes Th1 differentiation in aged BALB/c mice

We examined whether CpG‐DNA could be used as adjuvant to induce a T helper cell type‐1 (Th1) immunity in aged BALB/c mice that showed a Th2 polarization. Bordetella pertussis and complete Freund's adjuvant (CFA) were used as well. Immunization with ovalbumin (OVA)/CpG‐DNA showed that the immunoglobulin G (IgG)2a/IgG1 ratio and OVA‐specific T cell response were similar in young and aged mice. OVA/CpG‐DNA induced the secretion of interferon‐γ (IFN‐γ) and absence of interleukin (IL)‐5. Similar results were found in mice immunized with OVA/CFA. When mice were immunized with OVA/B. pertussis, we found that the IgG2a/IgG1 ratio and OVA‐specific T cell response were lower in aged mice and elicited IFN‐γ and IL‐5. In vitro CpG‐DNA stimulated antigen‐presenting cells to display IL‐12 and up‐regulate the expression of major histocompatibility complex class II and B7‐2 on B cells as efficiently in aged as in young mice, but the up‐regulation of B7‐1 was stronger i aged mice. The findings demonstrate that CpG‐DNA is able to induce a young‐like Th1 specific immune response in aged mice.