Cytokine messenger RNA expression in chronic inflammatory periodontal disease

It has previously been reported that, in periodontitis lesions, T cells with a memory/activated phenotype and with a type 2 cytokine profile accumulate in an oligoclonal fashion. Delineation of the role of cytokines in periodontal inflammation has, however, been complicated because of cross‐regulation and because of their overlapping and often redundant effects. The aim of this study was to examine messenger RNA levels for interferon γ, interleukin 4 (IL‐4), IL‐10, IL‐12 and IL‐13 in gingival tissues and peripheral blood mononuclear cells of patients with adult periodontitis. Reverse transcription polymerase chain reaction and subsequent image analysis was used to determine the level of mRNA for each cytokine. The mean expression of interferon γ mRNA was significantly higher in peripheral blood mononuclear cells than in gingival tissues. In contrast, the mean expression of IL‐10 mRNA was higher in gingival tissues than in peripheral blood mononuclear cells. This high expression of IL‐10 mRNA was, in fact, seen in only 7 gingival tissue samples with the majority of samples showing levels similar to peripheral blood mononuclear cells. There was no difference in the mean expression of IL‐12 p35 mRNA between gingival tissues and peripheral blood mononuclear cells. However, IL‐12 p40 mRNA was expressed higher in gingival tissues than in peripheral blood mononuclear cells in 6 out of 16 samples with significant difference of mean expression. Like IL‐10, gingival tissue samples and peripheral blood mononuclear cells expressed similar levels of IL‐12 p40 mRNA. There was no difference in the mean expression of IL‐13 in gingival tissues and peripheral blood mononuclear cells. Nevertheless, more peripheral blood mononuclear cell samples demonstrated high IL‐13 mRNA expression than gingival tissue samples. IL‐4 mRNA was weak but detectable in 3 gingival tissue samples. These results support the concept that cytokines form complex networks in periodontitis lesions and that their overlapping and redundant effects should be taken into account when considering the pathology of inflammatory periodontal disease. Dichotomous expression of IL‐10 and IL‐12 p40 mRNA in the periodontal lesion may be associated with disease entity.