Branched beta-1,3/1,6-glucans (scleroglucan) were produced by cultivation of Sclerotium rolfsii ATCC 15205. Regioselective hydrolysis at the beta-1,3-linkage of the cell-free and purified polysaccharide was performed in borosilicate glass bottles at pH 5, 121A degrees C, and 1 bar for 72 h. The mixture was divided into four molar mass fractions by stepwise cross-flow filtration using different cutoffs. In vitro studies revealed that scleroglucan hydrolysates with a low molar mass of less than 5 kDa significantly stimulated the activation and maturation of porcine monocyte derived dendritic cells (MoDC) by upregulation of CD40 and CD80/86 as well as by reduction of antigen uptake. MoDC treated with low molar mass scleroglucan showed a considerable increase in the amounts of secreted proinflammatory cytokine tumor necrosis factor alpha and stimulated the proliferation of lymphocytes. Therefore, scleroglucan molecules of low molecular weight are able to induce activation and maturation of porcine DC, which are key initiators of inflammatory and adaptive immune responses, and could provide improved protection against infectious diseases.