Fibroblasts, Mononuclear Phagocytes, and Endothelial Cells Express Monocyte Chemoattractant Protein‐1 (MCP‐1) in Inflamed Human Gingiva

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Abstract
Gingival inflammation is initiated by bacterial colonization of the tooth surface. It is characterized by infiltration of mononuclear cells, a feature of many forms of chronic inflammation. Monocyte chemoattractant protein‐1 (MCP‐1) is the predominant monocyte chemoattractant secreted by a variety of cells in vitro. We examined MCP‐1 expression in chronic gingival inflammation by double antibody immunohistochemistry that utilized rabbit anti‐MCP‐1 antibody simultaneously with mouse monoclonal antibodies to specific cellular markers. MCP‐1 mRNA expression by fibroblasts in inflamed gingival tissues was examined by in situ hybridization. We report here that in human chronic gingival inflammation the principal cell type expressing MCP‐1 in dense inflammatory infiltrates is the mononuclear phagocyte. The cells expressing MCP‐1 in moderately inflamed areas and in adjacent areas to inflammatory infiltrates are mononuclear phagocytes and fibroblasts, while in areas of fibroblastic hyperplasia, MCP‐1 positive cells are predominantly fibroblasts. We also demonstrate that in moderately and highly inflamed areas, the extent of MCP‐1 expression is greater than that in adjacent normal/mildly inflamed areas. As the degree of inflammation increased, there is also a concomitant increase in the number of mononuclear phagocytes. Furthermore, it is apparent that most of the infiltrating monocytes/macrophages are positive for MCP‐1 in vivo. Our finding that MCP‐1 expression is unambiguously identified in fibroblasts suggests that they can play a role in host defense by initiating the recruitment of monocytes. In addition, the expression of chemokines such as MCP‐1 may represent a mechanism for amplification of inflammatory signals in gingival inflammation. J Periodontol 1995; 66:80–88.