Peyer's patch-mediated intestinal immune system modulating activity of pectic-type polysaccharide from peel of Citrus unshiu

► An intestinal immune system modulating polysaccharide (CUI-3IIb-3-2, 18 kDa) was purified from Citrus unshiu peel. ► After enzymatic digestion of CUI-3IIb-3-2 and fractionation, CUI-3IIb-3-2 is assumed as pectic-type polysaccharide. ► Since enzymatic digest was lower the activity than CUI-3IIb-3-2, the whole structure was essential for the activity. ► When CUI-3IIb was orally administered in mice, the activity was significantly higher than a saline control.