Cystatin C-positive Macrophages and Dendritic Cells in the Rat Incisor Pulp

Abstract

Localization of cystatin C, an endogenous cysteine protease inhibitor, was examined in the dental pulp of rat incisors using immunofluorescence microscopy. Based on double labeling with ED1 and anti-cystatin C antibodies, it was determined that anti cystatin C-labeled cells were macrophages and/or dendritic cells. Furthermore, cells in the incisor pulp were characterized by triple labeling with anti-cystatin C antibodies, ED2 antibodies for resident macrophages and OX6 antibodies for MHC class II antigens. Three cysteine proteases, cathepsin B, L and S, were also examined with immunocytochemistry. The results showed, firstly, that cystatin C single-positive cells were localized in early apical pulp, and that these cells were presumably immature macrophages invading newly formed dental pulp. Secondly, about half of OX6⁺ cells in the middle and incisal pulp were ED2⁺, indicating that resident macrophages in addition to dendritic cells contribute to antigen surveillance via MHC Class II presentation. Thirdly, cathepsin S was present in cystatin C⁺ cells, and therefore they may be involved in formation of proteolytic environment in whole dental pulp. In conclusion, cystatin C-positive macrophages and possibly dendritic cells may play a role in regulating the proteolytic environment of the dental pulp as well as in immunological surveillance.