Production of proinflammatory and immunoregulatory cytokines by inflammatory cells from periapical lesions in culture

Background:  The role of cytokines in pathogenesis of periapical lesions is not well understood. The aim of this study was to study the correlation between proinflammatory and immunoregulatory cytokines in periapical lesions and their relationship with cellular composition and clinical presentation.
Methods:  Inflammatory cells were isolated from 67 human periapical lesions and cultivated for 24 h. The levels of proinflammatory cytokines: interleukin-1 beta (IL-1β), IL-6, IL-8 and tumour necrosis factor alpha (TNF-α) and immunoregulatory cytokines: transforming growth factor-beta (TGF-β) and IL-10 were determined in culture supernatants using a fluorescent bead immunoassay or ELISA. The phenotype of cells was analysed by immunocytochemistry.
Results:  Inflammatory cells from symptomatic lesions which contained higher proportion of granulocytes, secreted higher levels of IL-1, IL-6 and IL-8 compared with asymptomatic lesions. Large-size lesions contained lower percentages of mononuclear phagocytes, higher percentages of CD8⁺ T cells and produced higher levels of TNF-α, IL-6 and IL-10 compared with small-size lesions. There were negative correlations between the concentrations of TGF-β and proinflammatory cytokines. TGF-β, added to cultures, downregulated the levels of proinflammatory cytokines more strongly than IL-10, independently of clinical presentation of the lesions. By contrast, exogenous IL-10 was mainly immunosuppressive in cultures of asymptomatic lesions.
Conclusion:  Symptomatic lesions are characterized by higher production of proinflammatory cytokines. Immunoregulatory cytokines are more important for suppression of inflammation in asymptomatic lesions and in this context the effect of TGF-β is more potent and different from IL-10.