Immunohistochemical study on antigen-presenting cells in healthy and carious human teeth.

Class II major histocompatibility complex (MHC) antigen-presenting cells are associated with the early phase of the immune response. We have studied the distribution of class II-expressing cells in developing, healthy and carious human teeth to clarify, when human pulp acquires an immunologic defense potential and how this reacts to dental caries. Antigen-expressing cells were identified immunohistochemically with the following monoclonal antibodies: HLA-DR - for dendritic cells and CD68 - for macrophages. In the pulp of unerupted developing teeth, HLA-DR-positive cells were distributed mainly in and around the odontoblast layer. A few CD68 positive cells were located more coronary around the blood vessels. In erupted teeth, HLA-DR-positive cells were located, for the most part, just beneath the odontoblast layer. CD68 positive cells were also located coronary, mainly around the blood vessels. Superficial caries lesions caused an aggregation of HLA-DR-positive cells and macrophages in the dental pulp corresponding to the lesion. These findings showed that: (1) human teeth are already equipped with an immunological defense potential prior to eruption; (2) in the initial stage of caries infection, an immuno-response mediated by class-II-expressing cells is initiated in human dental pulp (Fig. 8, Ref. 33).