Figure 3.

Salmonella LPS-specific IgG responses were significantly decreased in IκBζ^−/− mice following oral administration of a RASV strain. Wild-type and IκBζ^−/− mice were immunised orally with 10⁹ CFU of a RASV strain per mouse twice at 2-week intervals (n > 3 per group). (A,B) The level of Salmonella LPS-specific Ab in serum was measured at 14 d after the second immunisation. To titrate the levels of LPS-specific IgG and IgG2a, LPS-specific IgG and IgG2a antibodies were measured from the serum of WT/PBS, IκBζ^−/−/PBS, WT/RASV and IκBζ^−/−/RASV mice 14 d after the second immunisation. ^**P < 0.01 and ^***P < 0.001 based on ANOVA with Bonferroni’s multiple comparison test. (C,D) The number of LPS-specific Ab-secreting cells isolated from spleen (C) and mesenteric lymph node (D) was measured by ELISPOT assay 14 d after the second immunisation with the RASV strain. (E) Splenic resting B cells were cultured in the presence of 12.5 µg/ml LPS plus 25 nM of retinoic acid (RA) and/or 0.2 ng/ml of TGF-β for 7 d to induce Ab class switching. Total IgG levels were measured by ELISA in the culture supernatant. Data are representative of three independent experiments. ^**P < 0.01 and ^***P < 0.001 based on unpaired t-test.