Several recent investigators have shed light upon the important role of TLR signaling in the development of mucosal inflammation (31) (32) (33) (34) . To understand how TLRs may signal within the epithelium, information may be gained by analyzing TLR signaling in other systems, primarily within leukocytes. A full description of the molecular mechanisms by which TLR signaling occurs is beyond the scope of this review; currently accepted concepts with respect to TLR signaling are described below (21, 35 have recent reviews).