An immunocytochemical study of the inflammatory cell infiltrate and epithelial expression of HLA-DR in odontogenic cysts.

The presence and distribution of lymphocytes, Langerhans cells, HLA-DR+ infiltrating cells and the expression of HLA-DR by lining epithelium was investigated in the walls of odontogenic cysts using an indirect immunoperoxidase method on acetone-fixed cryostat sections. The 23 cysts studied consisted of 14 dental (radicular) cysts, 5 keratocysts, 2 dentigerous cysts, 1 surgical ciliated cyst and 1 incisive canal cyst. The cell populations detected in the walls of all cysts were similar and consisted of HLA-DR+ macrophage-type cells and a mixture of T and B lymphocytes. Analysis of the T cell subsets revealed that in all cases the CD4+, Th/i subset predominated over the CD8+, Ts/c subset. 18/22 cyst linings contained cells expressing a Langerhans cell phenotype (CD1+). Cytoplasmic epithelial expression of HLA-DR was detected in 7/22 specimens. Neither the presence of HLA-DR+ epithelial cells nor LC were restricted to a given type of cyst. These findings indicate the occurrence of similar cellular processes irrespective of the proposed developmental or inflammatory aetiology of these lesions.