Fucoidan prevents C epsilon germline transcription and NFkappaB p52 translocation for IgE production in B cells.

Fucoidan, a dietary fiber contained in seaweed, reduces the increase of antigen-specific IgE in mice exposed to ovalbumin. In this study, we investigated the effect of fucoidan on IgE production and intracellular events in B cells in vitro. Fucoidan inhibited the production of IgE and C epsilon germline transcription in murine B cells induced by IL-4 (100 ng/ml) and anti-CD40 antibodies (10 microg/ml), whereas it stimulated cell proliferation. A significant effect of fucoidan on IgE production was observed when B cells were stimulated with a higher dose (5 microg/ml) of anti-CD40 antibodies, but not when stimulated with lower doses (1.25, 2.5 microg/ml), regardless of the IL-4 concentrations. Moreover, nuclear translocation of NFkappaB p52, but neither that of NFkappaB p65, nor the phosphorylation of JAK1 and STAT6 was reduced by fucoidan. These results suggest that fucoidan inhibited IgE production by preventing the NFkappaB p52-mediated pathways activated by CD40.