In this study, we hypothesized that restriction of carbon sources -specifically glucose- in the ASL is an important component of innate immunity. We report a mechanism responsible for a glucose concentration gradient generated by human airway epithelia resulting in low ASL glucose concentration, impaired bacterial growth, and airway sterility. Finally, we hypothesized that the higher susceptibility of hyperglycemic mice to infection is caused by elevated concentrations of glucose on the surface of the airway resulting in increased availability of glucose as a nutrient source for bacteria. We predicted that we would see no difference in bacterial growth if we used a mutant of PAO1 incapable of metabolizing glucose. Some artificially generated mutants or clinical strains of P. aeruginosa show variability in their capacity to preferentially use glucose as a carbon source, allowing to specifically AP24534 943319-70-8 assess the role of glucose in bacterial growth in vivo. We repeated the experiment using a transposon insertion mutant of PAO1 with a defective edd gene, which codes for phosphogluconate dehydratase, a protein required for the catabolism of glucose and gluconate to glyceraldehyde-3-phosphate and pyruvate via the Entner-Doudoroff pathway. In this study, we describe a novel mechanism that allows human airway epithelia to generate a transepithelial glucose concentration gradient. Moreover, this gradient results in an ASL that contains a low glucose concentration. Our studies suggest that this low concentration of glucose plays an important role in limiting the growth of bacteria and maintaining the sterility on the surface of human airway epithelia and leads us to speculate that the concentration of other carbon sources in ASL may also be low. We propose a novel mechanism in human airway epithelia that generates a transepithelial glucose concentration gradient by expressing 2 distinct facilitated diffusion transporters in polarized localizations. This is in contrast to mechanisms in epithelia of the human ileum or alveolar epithelia in the distal lung, where Na + glucose cotransport plays a central role in transepithelial glucose transport. GLUT-1, which we observed in the basolateral membrane, is the most ubiquitously expressed facilitated diffusion glucose transporter in humans; it has a Km between 3 and 7 mM and has a proposed function of cellular insulin-independent basal glucose uptake. GLUT-10, which we observed in the apical membrane of human airway epithelia, has previously been examined because of a potential link to Diabetes Mellitus Type 2, but studies failed to prove an association. Interestingly, GLUT-10 has a very low Km of approximately 0.3 mM, the lowest in the group of facilitated diffusion glucose transporters. This Km is very close to the glucose concentration in both human ASL and rat lung cells . Glucose is exclusively supplied to the airways from circulating blood, reaching the basolateral side of epithelial cells, where uptake of glucose can occur.