A team of Yale researchers has traced a path of cellular development that may lead to gastrointestinal and other ailments, including Creutzfeldt-Jakob disease, which is related to mad cow disease. The trail starts with the B cell, once thought capable only of producing serum antibodies and activating T lymphocytes. Now researchers have found that B cells are necessary for development of the M cell, an intermediary between the body and organisms in the gut. Only some of the M cell’s functions have been discerned. “M cells play a role in sensitizing the immune system to gastrointestinal flora,” said Mark Shlomchik, M.D., Ph.D., associate professor of laboratory medicine and immunobiology, “but they are also a portal of entry since many pathogens seem to enter the body through M cells.” The work, done in collaboration with a team at Jackson Labs, was published in the Dec. 2 issue of the journal Science.