Analysis of immune cells within the healthy oral mucosa of specific pathogen-free cats

The oral mucosa is an important interface for host-environment interactions. Based on previous studies, it is generally accepted that the cellular compartments of the oral immune system comprise organized mucosal-associated lymphoid tissues as well as diffusely and focally distributed T- and to lesser extent B-lymphocytes, oral mucosal Langerhans cells (OMLC), macrophages and mast cells. However, a comprehensive quantification of the cellular elements in the oral mucous membranes of the cat has not been reported. The aim of this study was to provide a comprehensive analysis of the immune cell compartments in the oral mucous membranes and anatomically related tissues of healthy cats. Multiple biopsies of the oral mucous membranes and related tissues were obtained from four specific pathogen-free cats for histological and immunohistochemical assessment of lymphocyte subsets, OMLC, macrophages and mast cells. T-lymphocyte subsets, OMLC, mast cells and macrophages were present in varying frequencies among the tissue compartments of the feline oral cavity. B-lymphocytes were not identified in any of the examined tissues except the tonsils and mandibular lymph nodes. Lymphocytic aggregates (follicles) were found in the palatoglossal folds and the gingiva. We describe the topographical distribution of various leucocyte subsets in the normal healthy feline oral mucosa, and demonstrate regional differences in the distribution of these cells.