A possible CD1a Langerhans cell–mast cell interaction in chronic hyperplastic candidosis

Aims:  T lymphocyte–antigen-presenting cell (APC) interaction plays a central role in T lymphocyte activation and APC maturation. We therefore studied the CD1a-positive Langerhans cells with respect to receptor activator of nuclear factor kappa B ligand (RANKL)-positive cells in chronic hyperplastic candidosis (CHC). Materials and methods:  Tissue sections of CHC were compared with leukoplakia and healthy oral mucosa using RANKL and CD1a monoclonal antibodies in an avidin–biotin peroxidase complex protocol. Two different antigen-retrieval protocols, pepsin preincubation and Tris–EDTA heat treatment, were used. Results:  CD1a-positive Langerhans cells were in healthy and leukoplakia epithelium found in the middle layer, but in CHC in all layers of the epithelium, at the basement membrane and as mononuclear round cells in the lamina propria. Use of pepsin digestion enabled studies of mast cells and their activation in the form of degranulation of RANKL. Conclusions:  The numerical, morphological and topographical versatility of the CD1a-positive Langerhans cells in CHC can be clarified by dendritic cell (DC) recruitment into the epithelium. RANK-positive and RANKL-sensitive DCs have ample opportunity to interact with local T lymphocytes. Use of an optimized antigen-retrieval protocol enabled demonstration of an active engagement (degranulation) of mast cells, which represent a rapidly available source of soluble RANKL.