Quantitative analysis of lymphocytes and their subsets in periapical lesions

The relative proportions of lymphocytes and their subsets in periapical lesions associated with untreated teeth and endodontically treated teeth were compared. Nine periapical lesions associated with previously untreated teeth and six persistent lesions associated with previously root treated teeth which had good quality root canal fillings and coronal seals were selected from a total of 41 samples. Clinical and radiographic features of each lesion were recorded. Serial frozen sections were stained using immunohistochemical methods and monoclonal antibodies against CD20, CD3, CD4 and CD8 to identify B, T, T helper (Th) and T suppressor (Ts) lymphocytes, respectively. Ten microscopic fields, representing the most dense cellular inflammatory infiltrate were selected per specimen and cell numbers were estimated, as a proportion of lesion area, using a point counting method. The periapical lesions associated with untreated teeth had a denser inflammatory cell infiltrate. The proportion of total lymphocytes was significantly higher in the untreated group of lesions (P < 0.01). The proportions of B (P < 0.01), T (P < 0.001) and Th cells (P < 0.01) were significantly higher in untreated teeth. The ratios of Th/Ts cells (P < 0.05) and T/total lymphocytes (P < 0.01) were also significantly different between the two types of lesion. The results show a difference in the inflammatory cell infiltrate and relative proportions of T, B and T helper cells in the two groups of lesions. This indicates that future studies of periapical lesions should take into account the clinical history of the associated teeth.