To observe the expression of interleukin-33 (IL-33) in macrophages of chronic periapical periodontitis and apical cyst tissue, and to provide a basis for the study of the pathogenesis of IL-33 in periapical diseases.

The apical tissues of 20 normal control group, 15 chronic periapical periodontitis group and 15 apical cyst group were collected for HE staining and optical microscopy respectively. CD14 was used as the marker of macrophages and double immunofluorescence staining was used to observe the changes of periapical tissues under fluorescence microscopy. The expression of IL-33 in CD14-positive macrophages was observed.

The macrophage density (cell/mm²) of IL-33 and CD14 positive expression in normal control group, chronic periapical periodontitis group and root cyst group were (23.81 ± 5.16, 62.97 ± 8.54, 119.83 ± 14.61) respectively, and there were significant differences among the three groups (F＝87.17, P < 0.01). The density of IL-33 and CD14 positive macrophages in root cyst group was significantly higher than that in chronic periapical periodontitis group and control group (P < 0.01).

IL-33 and CD14 positive macrophages increased in normal apical tissue, chronic periapical periodontitis tissue and apical cyst tissue in turn.