An activation on mouse bone marrow-derived dendritic cells (BMDCs) by low molecular weight oyster polysaccharides (LMW-OPS). BMDCs treated with LMW-OPS augmented allogeneic Th1 cell expansion. LMW-OPS induced significant increases in ERK and p38 MAPK phosphorylation in BMDCs. LMW-OPS induced activation of BMDCs in a MyD88-dependent and TLR 4-independent manner.