Objective To investigate whether R-848 could inhibit IgE production of mice immunized with OVA plus ALUM in vivo.Methods BALB/c mice were immunized s.c on the back with PBS,OVA,OVA plus R-848,OVA plus CpG,OVA plus ALUM,and OVA plus ALUM in R-848 or CpG every two weeks for three times.The blood from the mice was harvested after the last immunization,and the concentration of OVA specific or total IgE,IgG1 and IgG2a in the sera was determined;the splenocytes from the immunized mice were harvested and cultured with or without OVA for 3 days,and the concentration of IL-4 and IFNγ in the supernatants was determined.Results Firstly,we investigated that R-848 as Th1 adjuvant could enhance the production of OVA specific IgG2a in mice immunized with OVA.Secondly,further study showed that R-848 could inhibit the production of OVA specific IgE and total IgE,and promote the production of OVA specific IgG2a in the sera of mice immunized with OVA plus ALUM.Moreover,the results of ELISA showed that R-848 inhibiting IgE production was related to its reducing IL-4 production and enhancing IFNγ production.Conclusion R-848 could inhibit IgE production of mice immunized with OVA plus ALUM in vivo.