MUCOSAL CELL-MEDIATED IMMUNOLOGICAL CHANGES ASSOCIATED WITH EXPERIMENTAL GRAFT-VERSUS-HOST DISEASE

This study examined the histological changes and local cellular immune response induced within the lingual mucosa in an allogeneic Fl hybrid rat model of graft-versus-host disease (GvHD) with a view to studying oral lymphocyte-epithelial cell reactions. Highest levels of disease, as reflected by both a GvHD index and the extent of the oral mucosal changes, were obtained using primed donor (Lewis rats) splenocytes and irradiated hosts (Lew/Da rats). The lingual mucosae of test animals w ere characterised by irregular epithelial keratosis, an absence of bas al cell liquefaction and a diffuse inflammatory cell infiltrate, histo logical features consistent with an oral lichenoid tissue reaction. Im munohistochemical studies showed that mucosal involvement was characte rised by infiltration of the lamina propria by NK cells (CD8(+), CD5(- )), ''activated'' cells (CD25(+)) and T cells (CD5(+)) with selective migration of the latter, including a CD5(+), CD8(-) subset (helper/ind ucer T cell), into the epithelium. Epithelial expression of Ia was inv ariably associated with these inflammatory cell infiltrates and correl ated with the GVHD index. These findings suggest the presence of local mucosal T cell activation in the absence of detectable epithelial cel l damage, which may be equivalent to the early initiating events in th e pathogenesis of oral lichen planus. However, whilst experimental gra ft-versus-host disease appears to be a useful model for studying lymph ocyte-epithelial interactions, the induced oral mucosal changes are mo re consistent with a lichenoid reaction rather than lichen planus.