Langerhans cell dynamics in human gingiva during experimentally induced inflammation

The changes in the number of Langerhans cells within the gingiva during a 21 day experimental gingivitis episode were investigated immunohistochemically. Monoclonal antibodies to CD1a (specific for Langerhans cells and thymocytes) and HLA-DR (class II major histocompatibility antigens - (MHC)) were used to identify Langerhans cells within gingival biopsies taken on days 0, 7, 14 and 21. HLA-DR antibody stained dendritic cells within the oral epithelium which were morphologically identical to the CD1a+ Langerhans cells. Class II MHC LC numbers rose and plateaued between day 7 and 14 then decreased to baseline by day 21. As plaque accumulated and initial inflammation developed there was an increase in the number of CD1a+ Langerhans cells which peaked at day 7 and stayed high (day 14). As inflammation developed there was a statistically significant decrease in the number of CD1a+ Langerhans cells by day 21 (p = 0.028). The initial increase, followed by a decrease in CD1a+ Langerhans cells as inflammation developed, suggests that migration of Langerhans cells occurs within the gingival epithelium and this may represent an important early event in the gingival immune response to plaque.