IMMUNOHISTOCHEMICAL LOCALIZATION OF HLA-DR-POSITIVE CELLS IN UNERUPTED AND ERUPTED NORMAL AND CARIOUS HUMAN TEETH

Class II major histocompatibility complex (MHC) antigen-expressing cel ls are generally associated with the early phase of the immune respons e. We have studied the distribution of class II-expressing cells in de veloping, normal, and carious human teeth to clarify when human pulp a cquires an immunologic defense potential and how this reacts to dental caries. Antigen-expressing cells were identified immunohistochemicall y by means of HLA-DR monoclonal antibody. In the pulp of unerupted dev eloping teeth, numerous HLA-DR-positive cells were distributed mainly in and around the odontoblast layer. In erupted teeth, HLA-DR-positive cells were located, for the most part, just beneath the odontoblast l ayer, with slender cytoplasmic processes extending into the layer. Sup erficial caries lesions caused an aggregation of HLA-DR-positive cells in dental pulp corresponding to the lesion. In teeth with deeper cari es lesions, this aggregation of cells expanded to include the odontobl ast layer. Also noted were HLA-DR-positive cells lying along the pulp- dentin border, with cytoplasmic processes projecting deep into the den tinal tubules, where they co-localized with odontoblast processes. The se findings suggest that: (1) human dental pulp is equipped with immun ologic defense potential prior to eruption; (2) in the initial stage o f caries infection, an immunoresponse mediated by class-II-expressing cells is initiated in human dental pulp; and (3) HLA-DR-positive cells trespass deep into dentinal tubules as the caries lesion advances.