Immunocytochemically detectable metallothionein in granulation tissue surrounding mucosal ulceration.

Metallothioneins (MTs) are low-molecular-weight heavy metal binding proteins which are effective free oxygen radical scavengers in vitro. Free oxygen radicals have been implicated in the pathogenesis of stress-induced acute gastric mucosal ulceration and ischaemic injury in rat and man. Experimentally, MTs can have a protective role in stress-induced ulceration in rats. The possible cytoprotective role of MTs in chronic mucosal ulceration in man has not been previously studied. Evidence for locally produced MTs in human chronic gastric and small bowel ulcers has been sought by immunocytochemical staining using a monoclonal antibody (E9) to MT. At the base of ulcers MT has been localized to spindle cells (fibroblasts) in granulation tissue. Labelling of macrophages with a pan-macrophage marker KP1, and double labelling with KP1 and E9 showed two distinct populations, and MT appeared to be localized primarily in fibroblast-like cells.