AN IMMUNOHISTOCHEMICAL STUDY OF ORAL SUBMUCOUS FIBROSIS

Oral submucous fibrosis (OSF) is a chronic disease of the oral cavity characterized by inflammation and progressive mucosal fibrosis. These reactions may be the result of either direct stimulation from exogenou s antigens like areca alkaloids or by changes in tissue antigenicity t hat may lead to an autoimmune response. This study investigated the pr esence and distribution of inflammatory cells and MHC class II antigen expression by epithelial and immunocompetent cells using a three-stag e immunoperoxidase method on frozen sections. Thirty OSF tissue specim ens and ten normal buccal mucosae were studied and compared. All tissu es were investigated using antibodies to T cells (CD3), T helper/induc er cells (CD4), T suppressor/cytotoxic cells (CDS), B cells (CD20), na ive T cells and monocytes (CD45RA), macrophages, Langerhans' cells (CD 68) and HLA-DR-positive cells (HLA-DR alpha). The predominant cell pop ulations detect and HLA-DR-positive cells. The distribution of CD4-pos itive cells was similar to that of CD3-positive cells, which were scat tered, often uniformly distributed, both in the epithelium and connect ive tissue. CD8-positive cells were occasionally seen in the normal ep ithelium and lamina propria. Few scattered B cells (CD20) and macropha ges (CD68) were observed in normal mucosa. Naive T cells (CD45RA) were seen in all normal tissues focally concentrated around the connective tissue papillae, with a similar distribution to that of CD3-positive cells. All normal sections showed HLA-DR-positive cells scattered both in the epithelium and in the lamina propria. Epithelial cells did not show any positive reaction to this antibody and many intraepithelial positive cells showed a dendritic morphology. The cell populations det ected in OSF showed higher numbers of CD3 and HLA-DR-positive cells co mpared with those of the normal tissues. The pattern of staining for C D4-positive cells in OSF tissues was similar to that of CD3-positive c ells both in the epithelium and connective tissue and was higher than that in normal tissues. A few scattered CD8-positive cells and only oc casional CD20- and CD68-positive cells were seen in OSF sections. Few CD45RA-positive cells were found in the epithelium and lamina propria of OSF sections. However, OSF specimens showed high numbers of HLA-DR- positive cells in the basal layer of the epithelium, juxtaepithelium a nd in the lamina propria in a similar distribution to that of CD3 cell s compared with the normal tissues. Most HLA-DR-positive cells in the epithelium showed dendrites directed vertically towards the surface. T he increased evidence of CD4 and HLA-DR-positive cells in OSF tissues suggests that most lymphocytes were activated and shows an increased p resence of Langerhans' cells. The presence of these immunocompe tent c ells and high ratio of CD4 to CD8 in OSF tissues suggest an ongoing ce llular immune response leading to a possible imbalance of immunoregula tion and alteration in local tissue architecture.