A bacterial macromolecular complex produced by bacteria belonging to the Bifidobacterium longum strain deposited according to the treaty of Budapest under number CNCM I-3994 with the Collection Nationale de Cultures de Microorganismes (CNCM) [National Collection of Microorganism Cultures], consisting of chains combining a lipoprotein and an oligosaccharide, wherein:the lipoprotein has a molecular weight of from 30 kDa to 60 kDa；the oligosaccharide has a molecular weight of less than 15 kDa, and preferably less than 10 kDa；the lipoprotein component, which consists of all the lipoproteins of each of the chains, represents from 75 to 99%, preferentially from 80 to 98%, more preferentially from 85 to 95% by weight of the total weight of the complex, and the oligosaccharide component, which consists of all the oligosaccharides combined with each of the chains, represents from 1 to 25%.
