Abstract • 16a

Human milk oligosaccharides (OS) inhibit many enteropathogens common in infants. Human milk OS patterns vary between individuals, and for the same individual over the course of lactation. Due to common mechanisms of synthesis between human milk OS and cell surface glycoconjugates, human milk OS might also be expected to vary with blood type. OS were isolated from the milks of 76 mothers in early lactation, reduced, and separated into acidic and neutral fractions. The neutral OS were perbenzoylated, and quantitative reversed phase HPLC revealed compounds ranging from tri- to octasaccharides. Earlier, we had found that a high α1,2 to α1,3 ratio during early lactation is characteristic for the majority of milk donors. In the current samples, concentrations of OS containing α1,2 fucosyl linkages were also higher than those containing α1,3 fucosyl linkages, and for about 40% this ratio was greater than 10:1. Concentrations of 2′-FucLac and LNF-I did not vary significantly between the three Lewis blood groups in this study. However, concentrations of 3-FucLac and LNF-II,III were significantly lower in the Le(a-b-) population than in the Le(a+b+) or (a-b+) groups, a result not predicted by previous studies of differential expression of milk oligosaccharides by Lewis blood group type. The ratio of the concentrations of (2′-FucLac plus LNF-I) to those of (3-FucLac plus LNF-II,III) was much larger for Le(a-b-) donors than it was for either Le(a+b+) or Le(a-b+) donors. The hexasaccharides LDFH-I and LDFH-II occurred in higher amounts in the milks of Le(a-b+) and (a+b+) donors than in those of the Le(a-b-) individuals. These differences were present irrespective of A, B, or O status, there was no relationship between Lewis blood group types and the absolute presence or absence in the milks of oligosaccharides containing Fuc α1,2 α1,3 or α1,4 linkages. Milks representing all the blood groups in this study contained all the major neutral human milk oligosaccharides--only the relative concentrations varied. Genetically based individual differences in the expression of oligosaccharides in human milk suggests innate individual variation in the ability of nursing mothers to protect their infants from specific pathogens. Funded by HD13021 Shriver Center for Mental Retardation, Waltham, MA 02452 and Harvard Medical School, Boston, MA; Instituto Nacional de Nutricion, Mexico City, Mexico.