FACTOR XIIIA-POSITIVE DENDROCYTES ARE INCREASED IN NUMBER AND SIZE INRECURRENT APHTHOUS ULCERS (RAU)

The factor XIIIa-positive (FXTIIa+) cell is a potent antigen-presentin g cell, which has been described as increasing in numbers in various c hronic inflammatory conditions. The purpose of this study was to inves tigate the distribution and frequency of FXTIIa+ cells in acute recurr ent aphthous ulcer (RAU) lesions compared with induced traumatic ulcer (TU) lesions and with clinically healthy oral mucosa. Samples were la beled with polyclonal rabbit anti-human FXIIIa antibodies in avidin-bi otin-peroxidase complex (ABC) staining. Most of the FXIIIa-immunoreact ive cells in TUs and normal mucosa were spindle-shaped, whereas a rela tively large, dendritic-like cell was predominant in RAU lesions. FXII Ia+ cells were quite frequent within mononuclear cell-rich inflammator y cell infiltrates and in perivascular areas in RAU lesions. In contra st, FXIIIa+ cells were not found in mucosal epithelium or in the neutr ophil-rich areas. RAU mononuclear cell-rich inflammatory cell infiltra tes appeared to have greater numbers of positively stained cells than the TU-inflammatory cell infiltrates (199+/-67 vs 110+/-31 cells/mm(2) , P<0.001). Overall, FXIIIa+ dendrocytes were increased in numbers, an d apparently also in size, in RAU lesions (274+/-68/mm(2)) as compared to controls (177+/-74/mm(2), P<0.01), and to TU lesions (183+/-50 mm( 2), P<0.01). Interestingly, relatively high numbers of FXIIIa+ dendroc ytes were also found in deep connective tissue in RAU sections compare d with TUs (281+/-80 vs 166+/-57, P<0.01). The characteristic changes in the size and shape of individual FXIIIa+ cells, their typical distr ibution and increase in frequency in RAU lesions indicate active invol vement in the local pathogenic mechanisms. Localization to perivascula r areas/inflammatory cell infiltrates would be compatible with a role in antigen presentation.