Identification and Phylogeny of the First T Cell Epitope Identified from a Human Gut Bacteroides Species.

Host T cell reactivity toward gut bacterial epitopes has been recognized as part of disease pathogenesis. However, the specificity of T cells that recognize this vast number of epitopes has not yet been well described. After colonizing a C57BL/6J germ-free mouse with the human gut symbiotic bacteria Bacteroides thetaiotaomicron, we isolated a T cell that recognized these bacteria in vitro. Using this T cell, we mapped the first known non-carbohydrate T cell epitope within the phylum Bacteroidetes. The T cell also reacted to two other additional Bacteroides species. We identified the peptide that stimulated the T cell by using a genetic approach. Genomic data from the epitope-positive and epitope-negative bacteria explain the cross-reactivity of the T cell to multiple species. This epitope degeneracy should shape our understanding of the T cell repertoire stimulated by the complex microbiome residing in the gastrointestinal tract in both healthy and disease states.

Quantification of prenatal exposure and maternal-fetal transfer of nonylphenol.

Nonylphenol (NP) is an environmental hormone commonly found in daily foodstuffs. This study examined maternal and umbilical-cord blood samples to explore prenatal exposure levels to nonylphenol and placental protection against NP exposure. One hundred and seventy-four mixed cord blood samples were collected. Among them, 42 pairs of expectant mothers and their prenatal fetus were matched to compare nonylphenol levels between mothers and fetuses. An additional 30 mother-infant dyads were chosen to give maternal, umbilical arterial and venous blood samples. Plasma samples were enzymatically deconjugated and then cleaned up with solid-phase extraction. After extraction, samples were analyzed with reversed-phase high-performance liquid chromatography coupled with fluorescence detection. Analytical results identified prenatal exposure to NPs and relatively high prenatal exposure levels in metropolitan areas. The concentrations ranged from undetectable (below 1.82 ng/g plasma) to 211 ng/g plasma. Concentrations of NP in mother-infant dyads showed the NP concentrations in maternal plasma were not definitely higher than that in fetal plasma. Still, 63.6% of NP detectable mother-infant dyads showed a higher concentration in umbilical venous plasma than those in umbilical arterial plasma. Through the repeated exposure from expectant mothers' dietary intake, fetuses could encounter high NP exposure level due to transplacental absorption, partitioning between the maternal and fetal compartments, as well as poor detoxification mechanisms of the developing organism. Some mechanisms may contribute to the reduction of NP levels in fetal blood circulation but those remain unclear.