Characterization of cells containing factor XIII subunita in benign and malignant buccal lesions

Summary In the present study, the distribution pattern and characteristics of cells containing Factor XIII subunita (FXIII A) have been studied in benign and malignant lesions of human buccal mucosa. Tissues from four irritation fibromas and three squamous cell carcinomas were studied by means of double immunofluorescent staining techniques in which the detection of FXIII A was combined with a reaction with CD14 (recognizing a monocyte/macrophage differentiation marker antigen), Mac 387 (reacting with a special subset of macrophages), anti-HLA-DR, Ki-M7 (labelling phagocytosing macrophages) or Ki-67 (visualizing a nuclear antigen associated with cell proliferation) monoclonal antibodies. FXIII A was detected in cells of the connective tissue stroma in both benign and malignant buccal lesions. The number of these FXIII A-reactive cells (FXIII A⁺ cells) increased considerably in the tumour tissues, in particular in those surrounding tumour cell clusters. FXIII A⁺ cells scattered in the fibromatous tissues were spindle-shaped, whereas in the tumour stroma, large stellate cells predominated, and round cells were likewise labelled around blood vessels. FXIII A⁺ cells were labelled with CD14 and Ki-M7 in both fibromatous and tumoural buccal mucosa; however, they failed to show any reaction with Ki-67. FXIII A⁺ cells accumulated in the tumour stroma reacted for HLA-DR as well. These results indicate that in both the benign and malignant buccal lesions FXIII A is contained in a subpopulation of tissue macrophages, which represents a monocyte-derived (CD14⁺) and phagocytosing (KiM7⁺) cell population. The accumulation of the FXIII A⁺ cells in the tumour stroma is believed to be a result of direct migration from the circulating blood. The FXIII A⁺ cells of the tumour stroma may be actively involved in both antigen presentation and matrix remodelling during tumour progression.