M2 macrophages coexist with a Th1-driven profile in periapical cysts

To evaluate the participation of both Th1 and Th2 responses in periapical cysts by assessing the presence of M2 macrophages, as well as acute IL-1 β, TNF-α and IL-6 cytokines.

Twenty-four cases of periapical cysts were selected. Immuno-expressions of IL-1 β, IL-6, TNF-α and CD163 were analysed in the cystic capsules in both superficial and deeper regions. Data were analysed with paired Wilcoxon test and Spearman correlation coefficient (P ≤ 0.05).

There was a higher expression of IL-1β, IL-6, TNF-α and M2 macrophages in the superficial region (P < 0.001) of cystic capsules. All acute cytokines had significant positive correlations amongst them regardless of the cystic capsule region. Regarding CD163, positive correlations occurred only with TNF-α (P = 0.007; r = 0.537) and IL-6 (P = 0.018; r = 0.478) in the superficial regions of the cystic capsule.

M2 macrophages participated actively in the inflammatory response of periapical cysts and correlated with the expression of certain acute Th1-related cytokines. This illustrates the coexistence of an acute and chronic Th2-driven immune response in these lesions. Although M2 macrophages favour the healing process, their presence is not sufficient for periapical cyst regression, once an acute active response has occurred due to an infectious stimuli.