Bacteroides species are some of the most common bacteria in the human gut. Enviornmental Health Perspectives hide caption

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Even in the remote Faroe Islands, some children have high levels of perfluorinated compounds in their blood. The chemicals may interfere with the immune system. Stig Nygaard/Flickr hide caption

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Dr. Ralph Steinman of Rockefeller University died Friday, three days before he was named a winner of the Nobel Prize in Physiology or Medicine for "his discovery of the dendritic cell and its role in adaptive immunity."

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