T lymphocyte activation and cytokine expression in periapical granulomas and radicular cysts

Introduction

Radicular cysts (RCs) are periapical lesions resulting in jaw bone destruction. The inflammatory dental periapical granuloma (PG) is considered to be the origin of RC formation; however the mechanism of RC development remains unclear.

Methods

Cell suspension from the surgically extirpated tissue of 27 RCs and 25 PGs was obtained. Bacteriological analysis of the PG tissue samples was performed in order to define two major groups of PG according to the prevailing causative bacterial infection: the streptococcal PG (PG-S, n = 10) and the anaerobe PG (PG-A, n = 9) group. The inflammatory response of tissue infiltrating lymphocytes was assessed by following T lymphocyte activation (HLA-DR expression) as well as interferon γ (IFN-γ) and interleukin 4 (IL-4) production which were evaluated by the flow cytometry.

Results

In comparison to RC both types of PG contained a higher proportion of activated T cells (HLA-DR) and lower proportion of IL-4 producing cells. PG-A tissue contained increased percentage of CD3 cells and increased percentage of T helper 1 (Th1) cells in comparison with PG-S. In RC the IFN-γ production is higher than in streptococcal PG-S but similar as in PG-A.

Discussion

Tissue infiltration by Th2 cells and IL-4 production is likely to play an etiopathogenic role in RC formation.