Lipoteichoic Acids fromLactobacillus johnsoniiStrain La1 andLactobacillus acidophilusStrain La10 Antagonize the Responsiveness of Human Intestinal Epithelial HT29 Cells to Lipopolysaccharide and Gram-Negative Bacteria

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Abstract
Intestinal epithelial cells (IECs) respond to lipopolysaccharide (LPS) from gram-negative bacteria in the presence of the soluble form of CD14 (sCD14), a major endotoxin receptor. Since sCD14 is also known to interact with gram-positive bacteria and their components, we looked at whether sCD14 could mediate their effects on human IECs. To this end, we examined the production of proinflammatory cytokines following exposure of the IECs to specific gram-positive bacteria or their lipoteichoic acids (LTAs) in the absence and presence of human milk as a source of sCD14. In contrast to LPS fromEscherichia coliorSalmonella enteritidis, neither the gram-positive bacteriaLactobacillus johnsoniistrain La1 andLactobacillus acidophilusstrain La10 nor their LTAs stimulated IECs, even in the presence of sCD14. However, both LTAs inhibited the sCD14-mediated LPS responsiveness of IECs. We have previously hypothesized that sCD14 in human milk is a means by which the neonate gauges the bacterial load in the intestinal lumen and liberates protective proinflammatory cytokines from IECs. The present observations suggest that gram-positive organisms, via their LTAs, temper this response and prevent an exaggerated inflammatory response.

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