The kinetic organization of the ulcer-associated cell lineage (UACL): delineation of a novel putative stem-cell region.

We have examined the proliferative organization of the ulcer-associated cell lineage (UACL), in a series of human ileal tissues involved by Crohn's disease, using antibodies to trefoil peptides and Ki-67. The UACL arises in conjunction with endodermal damage and is likely to play a role in subsequent tissue repair. Our study supports the view that the UACL initially forms through extrusion from the base of a parent intestinal crypt without indigenous mitotic activity. Eventually a duct forms extending to the gut surface and within this duct a proliferative zone develops. We also confirm that the trefoil peptides pS2 and hSP, which play a major role in the repair process, are spatially segregated within the UACL with a zone of overlap in the duct. Using triple antibody labelling techniques we have demonstrated that the zone of overlap of these peptides coincides with the proliferative region and provides evidence for a novel stem cell zone.