Critical design aspects involved in the study of Paneth cells and the intestinal microbiota.

Paneth cells are long-lived secretory cells that reside in the base of the crypts of Lieberkühn of the small intestine. They produce an arsenal of molecules that are involved in numerous biological processes, ranging from the control of gut microbial populations to supporting the intestinal stem cell niche. Because of these important functions, Paneth cell abnormalities are becoming implicated in a variety of disease processes. As such, it is necessary to establish parameters that will allow for the comprehensive study of Paneth cells in health and disease. In this addendum, we highlight critical design aspects involved in the study of Paneth cells and their downstream effects on the intestinal microbiota. The importance of this approach is demonstrated by our recent findings that Nod2 does not regulate mouse Paneth cell antimicrobial function, in contrast to previous reports. This work defines key issues to consider when studying Paneth cells in mouse systems.