EXPRESSION OF INFLAMMATORY CYTOKINE GENES IN-VIVO BY HUMAN ALVEOLAR BONE-DERIVED POLYMORPHONUCLEAR LEUKOCYTES ISOLATED FROM CHRONICALLY INFLAMED SITES OF BONE-RESORPTION

Alveolar bone-derived polymorphonuclear leukocytes (PMNs) were charact erized for their ability to produce inflammatory cytokines such as int erleukin-1 alpha (IL-1 alpha), IL-1 beta, tumor necrosis factor alpha( TNF alpha), and IL-6 in vivo. Periapical exudates (PE) were collected from periapical lesions with chronic periapical periodontitis through root canals. Cells and noncellular supernatants were then isolated by centrifugation. The concentration of cytokines present in the noncellu lar supernatants were determined by ELISA. High concentrations of IL-1 alpha, IL-1 beta, and IL-6 were detected in PE, however, TNF alpha wa s not. PE contains predominantly PMNs (>95% of residing cells) with a few percent of lymphocytes and/or macrophages. These alveolar bone-der ived PMNs were purified by the Ficoll-Hypaque gradient method and were analyzed for cytokine mRNA expression using the cytokine-specific rev erse-transcription polymerase chain reaction. Highly purified PMNs (>9 9.5%) isolated from PE expressed significant levels of mRNA for IL-alp ha, IL-1 beta, and TNF alpha. IL-6 mRNA was not detected, although a h igh concentration of IL-6 was detected in supernatants of PE by ELISA. The IL-6 secretion in PE could be derived from macrophages, T lymphoc ytes, osteoblasts, or fibroblasts around periapical lesions. These dat a strongly suggest that human PMNs derived from alveolar bone can spon taneously produce IL-1 alpha, IL-1 beta, and TNF alpha at sites of inf lammation, and probably initiate inflammation and regulate augmentatio n of bone resorption in vivo.