The infant formula used as a control in this study contained galactooligosaccharides which are also added to infant formulas in an effort to functionally mimic HMO. GOS are heterogeneous mixtures of isomers and chain lengths and we did not have the methodology to Emodin identify structures in urine or plasma that could be conclusively attributed to the ingestion of GOS by formula fed infants. Additionally, we did not identify major MW signals that would suggest that GOS were detected in our analyses. Halopemide Neutral HMOs have been shown to be transported across the intestinal epithelium by receptor-mediated transcytosis as well as via paracellular pathways, and have been measured in the intracellular compartment. Acidic glycans seem to be translocated only via paracellular flux. Eiwegger showed a 4�C14% uptake of neutral HMOs across the intestinal epithelium. Milk oligosaccharides have also been hypothesized to be taken up directly from the gut lumen by dendritic cells. In addition to demonstrating the intestinal absorption of HMOs and the likely mechanisms involved, these data indicate that at least some milk glycans are available at the intracellular level where they have the potential to directly modulate cell signaling. Similar to our data, several studies in exclusively breastfed infants found urinary HMO profiles resembling those of the mothers�� milk and a renal excretion of 1�C3% of individual HMOs. Several of these studies used a bolus of 13C-labelled galactose fed to lactating women and showed the 13C-Gal to be directly incorporated into the mothers�� breast milk oligosaccharides. These 13C-HMOs were then detected in the infants�� urine, reaching peak levels at 8�C12 hours after the mothers were fed, and were still detectable 36 hours later. This suggests that HMOs from mother��s milk may stay in infant��s circulation for several hours after absorption before being excreted via urine. Additionally, variations in retention time in the infant suggest that neutral and acidic HMOs may be utilized differentially. There is increasing evidence that milk glycans provide specific benefits to the immune system and neuronal development of the breastfed infant. In order to exert systemic effects however, HMOs must be absorbed and transported in the peripheral blood to specific cells where they might interact.