The distribution and ultrastructure of class II MHC-positive cells in human dental pulp

Abstract

The distribution and ultrastructure of class II major histocompatibility complex (MHC)-positive cells were investigated in human dental pulp, employing immunohistochemistry using an anti-human leukocyte antigen (HLA)-DR-monoclonal antibody. HLA-DR-immunopositive cells, appearing spindle-like or dendritic in profile, were densely distributed throughout the dental pulp. Under the electron microscope, these cells exhibited various sizes of vesicles containing clear or opaque contents, multivesicular bodies and characteristic fine tubulovesicular structures in their cytoplasm. Some reactive cells possessed coated pits and vesicles including electron-dense materials, indicating an active endocytosis. At the periphery of the pulp tissue, the HLA-DR-immunopositive cells were predominantly situated in the subodontoblastic layer, with some located in the odontoblast layer and/or predentin and extending their cytoplasmic processes into the dentinal tubules. Cell processes of these cells occasionally made contact with several odontoblast processes in the same way as the nerve fibers in the predentin. These cells never contained the typical phagosomes frequently observed in the HLA-DR-immunoreactive macrophages in the subodontoblastic layer and the pulp core. The results suggest that the HLA-DR-immunopositive cells in the odontoblast layer and/or predentin have some regulatory function on the odontoblasts under physiological conditions, in addition to their involvement in the initial defense reaction after tooth injury.

Pulpal regeneration after cavity preparation, with special reference to close spatio‐relationships between odontoblasts and immunocompetent cells

“…These class II MHC-positive cells along the pulp-dentin border were characterized by tubulovesicular structures and multivesicular bodies, as categorized in the pulpal dendritic cells described above (Ohshima et al, 1994(Ohshima et al, , 1999. This phenomenon may be explained by the idea that the pulpal dendritic cells respond actively to bacterial or noxious substances derived through the exposed dentinal tubules, as we have suggested .…”

“…Interestingly, under experimental conditions, the class II MHC-positive cells have been suggested to have diverse functions in odontoblast differentiation in the rat dental pulp in addition to ordinary antigen presentation . Under physiological conditions, furthermore, class II MHC-positive cells in the human odontoblast layer and/or predentin might have some regulatory function in the homeostasis of odontoblasts (Ohshima et al, 1999). These findings, therefore, lead us to the possibility that the immunocompetent cells play an important role in the process of pulpal healing after cavity preparation.…”

Adaptive Calcified Matrix Response of Dental Pulp to Bacterial Invasion Is Associated with Establishment of a Network of Glial Fibrillary Acidic Protein+/Glutamine Synthetase+ Cells

“…13 Although the function of these cells is not clearly understood, anatomical proximity and functional coupling through gap junctions implies a regulatory role. 14 Interodontoblastic cells could be involved in the response of odontoblasts to bacterial challenge, and they may be necessary for an integrated response to bacterial invasion.…”

Appearance and distribution of dendritic cells and macrophages in dental pulp during early postnatal morphogenesis of mouse mandibular first molars

“…Dendritic cells show no or little activity of acid phosphatase (ACP), whereas macrophages have phagocytic capability and exhibit ACP activity that is dependent on the phagocytic capability (Steinman et al 1986). Class II MHC antigen-expressing cells have been identified in the dental pulp of humans and rats by immunohistochemistry using HLA-DR and OX-6 antibodies (Jontell et al 1987(Jontell et al , 1988(Jontell et al , 1991(Jontell et al , 1994Ohshima et al 1994Ohshima et al , 1995Ohshima et al , 1999Okiji et al 1994Okiji et al , 1996Okiji et al , 1997Yoshiba et al 1996). Based on the criteria of the expression of class II MHC antigens and the activity of ACP, previous studies have indicated that, whereas macrophages are present in the central region of the dental pulp, dendritic cells are located in and around the odontoblastic layer.…”

“…The immunological aspects in pulpal tissue and the putative function of these cells were reviewed by Jontell et al (1998). It has been suggested that the class II MHC-expressing dendritic cells in the odontoblastic layer may regulate the function of odontoblasts and play a role in odontoblast differentiation in human and rat teeth (Ohshima et al 1995(Ohshima et al , 1999, and class II MHC-positive cells have been suggested to play an inductive role in differentiation, migration, and/or activation of odontoblasts and cementoblast-like cells during the resorption stage of human deciduous teeth (Kannari et al 1998). In addition, age-related change and delayed appearance of class II MHC-positive cells have been reported in dental pulp during development of rat incisors and molars (Jontell et al 1991;Okiji et al 1996).…”