Human milk oligosaccharides: a novel method provides insight into human genetics

Human milk is a unique reservoir of oligosaccharides. The presence of many of these oligosaccharides is determined genetically and is related to the Lewis blood group and secretor antigen status of each donor. A method to quantitate neutral human milk oligosaccharides was developed. Sample preparation was based on a single centrifugation-filtration step that yields oligosaccharide extracts. These extracts first were fractionated to remove a significant portion of their lactose content and were analyzed using high-pH anion-exchange chromatography. Oligosaccharide profiles from 386 milk samples obtained in this fashion generated quantitative information on lactose, the neutral cores lacto-N-tetraose (LNT) and lacto-N-neotetraose (LNneoT), and the key fucosylated oligosaccharides. Additionally, the profiles provided genetic footprints of the Lewis and secretor status of the donors. Furthermore, unusual profiles that could not have been predicted from known genotypes were found. For this reason, milk glycoproteins were studied using carbohydrate-binding probes. Results confirm that oligosaccharides are an accurate predictor of the Lewis blood group status of the donor, and that glycosyltransferases have exquisite specificities. The data obtained in this study corroborate that Lewis-related antigens are tissue specific. This attribute of immunodominant carbohydrate sequences has significant implications for epidemiological studies of breast-fed infants.