Detection and characterization of interleukin-1 in human dental pulps

Pulp tissue was obtained from clinically intact third molars and premolars, and from teeth affected by caries and periodontal disease. After incubation and homogenization, supernatants were centrifuged, sampled and assayed for lymphocyte activating factor-like activity using the thymidine-incorporated D10.G4.1 cell-line assay. Significantly higher levels of mitogenic activity were found in the pulp supernatants of symptomatic carious teeth, and in those of third molars with attendant pericoronitis, than in pulps from symptomatic and asymptomatic periodontally affected teeth and asymptomatic third molars and premolars. As both interleukin-1 (IL-1) and interleukin-2 (IL-2) may be involved in the proliferation of D10.G4.1 cells, supernatants from carious pulps were further tested for IL-2 activity using murine natural killer (NK) cells. Those that had elicited a proliferative response of D10.G4.1 cells did not enhance NK proliferation, indicating that the factor responsible for clonal replication of D10.G4.1 cells was IL-1. To confirm the presence of IL-1, immunohistochemistry using a monoclonal antibody to IL-1 was performed on frozen and paraffin-embedded sections of pulps from each group. IL-1 was immunolocalized within cells in pulps from the caries symptomatic group. The cell type producing IL-1 was further characterized as an alpha-naphthyl-acetate-esterase-positive macrophage within the connective tissue stroma of pulps from the caries symptomatic group. This novel demonstration of IL-1 and IL-1 producing cells in human dental pulp indicates the involvement of this mediator of inflammation in dental disease.