Role of CpG ODN in concanavalin A-induced hepatitis in mice

OBJECTIVE: To investigate the effects of an intradermal injection of oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs on concanavalin A (Con A)-induced hepatitis, an experimental model of immune-mediated hepatitis. METHODS: Con A was injected intravenously into Balb/c mice. Twelve hours after Con A challenge, blood and liver samples were obtained. CpG ODN was injected intradermally 48 hours before Con A challenge. The extent of liver injury was assessed by determining serum alanine transaminase (ALT) and by liver histology. Serum levels of cytokines, including interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, interleukin (IL)-4 and IL-5, were measured by enzyme-linked immunosorbent assay. RESULTS: Co-administration of Con A and CpG ODN significantly increased serum ALT in mice compared with that in the case of administration of Con A alone (10,268 +/- 4,654 and 1,140 +/- 832 IU/1, respectively, p<0.05). In liver histology, mice treated with CpG ODN and Con A showed more extensive midzonal necrosis than did mice treated with Con A alone. These mice also showed significant increases in serum TNF-alpha and IFN-gamma and decrease in serum IL-5. CONCLUSIONS: The results indicate that CpG ODNs aggravate Con A-induced hepatitis by stimulating the production of T-helper-1 (Th1) cytokines, TNF-alpha and IFN-gamma, suggesting that bacterial DNA that contains unmethylated CpG motifs may contribute to the exacerbation of immune-mediated liver injury.