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

Dendritic cells and macrophages were examined in dental pulp during the pos tnatal development of mouse mandibular first molars, by immuno- and enzyme histochemistry. F4/80 antibody against dendritic cells and macrophages demo nstrated labeled cells predominantly in and around the odontoblastic layer during tooth development from postnatal day 0 (PN0) to PN5. Labeling with M ac-1, Mac-2, and MOMA-2 antibodies against macrophages showed varied distri bution patterns. Mac-1-positive cells were not detected in the dental pulp. Mac-2-positive cells appeared in the dental pulp at PN0, but not in or aro und the odontoblastic layer, and disappeared by PN3. A few MOMA-2-positive cells were detected in the dental pulp during the period examined. The F4/8 0-positive cells in and around the odontoblastic layer did not exhibit acid phosphatase or nonspecific esterase activities. In addition, the F4/80-pos itive cells showed continued expression of Fc gamma receptor, but not class II major histocompatibility complex (MHC). Other antibodies against dendri tic cells (NLDC-145, MIDC-8, and 33D1) did not label the F4/80-positive cel ls. We concluded that the F4/80-positive and class II MHC-negative cells in and around the odontoblastic layer may be immature dendritic cells in the early stages before eruption, weaning, and crucial exposure to antigenic st imuli. They may not only act primarily as immunosurveillance cells, but als o play a role in a regulatory function and differentiation of odontoblasts.