Mast cell-deficient mice exhibit diminished intestinal responses to Clostridium difficile toxin A: Evidence that mast cells and substance P contribute to toxin A-induced inflammation: B.K. Wershil, I. Castagliuolo, J.T. LaMont, C. Pothoulakis. The Combined Program in Pediatric GI/Nutrition, Harvard Med. School, and Section of GI, Boston University, Boston, MA