Localization and density of myeloid leucocytes in the periodontal ligamentof normal rat molars

The phenotypic distribution and density of macrophage-associated antigen-ex pressing cells in the periodontal ligament (PDL) of normal rat mandibular f irst molars was evaluated by immunohistochemistry, and an attempt made to i dentify dendritic cells (DCs) by immunoelectron microscopy. Cells immunopos itive to ED1 (a general macrophage marker) were widely distributed througho ut the PDL and were most common around blood vessels. A small number of T l ymphocytes and OX62 (anti-veiled cells and gamma delta T cells)-positive DC -like cells were also found. The relative density of cells immunopositive t o ED9 (CD14), OX42 (CD11b), OX6 (anti-class II MHC molecules), ED2 (anti-ti ssue-resident macrophages), 8A2 (CD11c) and WT.1 (CD11a) varied in the mesi al, distal and periapical regions of the distal root and the furcal region. This finding suggests that there are several subpopulations of ED1-positiv e cells which express various combinations of these markers. Immunoelectron microscopy revealed that a small, but distinct, subpopulation of ED1- and OX6-positive cells did have a DC-like ultrastructure, although the majority of these cells were identified as macrophages. The DC-like cells were char acterized by poorly developed lysosomal structures and an absence of phagoc ytic vesicles. It was concluded that the normal rat PDL is equipped with he terogeneous populations of macrophages with regional variations in density. The DC-like cells may function as antigen-presenting cells. (C) 2001 Elsev ier Science Ltd. All rights reserved.