Expression of Helper and Regulatory T Cells in Atopic Dermatitis: A Meta-Analysis

Atopic dermatitis (AD) is a common inflammatory skin disease, with the incidence peaks in infancy. A meta-analysis was performed to assess the levels of T helper type 22 (Th22) cells, T helper type 17 (Th17) cells, interleukin (IL)-17, and Tregs in peripheral blood of patients with AD.A comprehensive literature search was performed in PubMed, Embase, China National Knowledge Internet, and Wan-fang Data from the day of inception of this study to July 2021. Two authors independently extracted the data, which were pooled and calculated using Stata software version 15.A total of eight studies met the inclusion criteria. Compared with control group, patients with AD had an increased proportion of Th22 cells [weighted mean difference (WMD) = 2.07, 95% CI (1.33, 2.81), p < 0.001], Th17 cells [WMD = 1.04, 95% CI [0.66, 1.43], p < 0.001], IL-17 [WMD = 17.56, 95% CI (11.1, 24.03), p < 0.001], and a decreased proportion of Tregs [WMD = -2.49, 95% CI (-2.93, -2.05), p < 0.001] in peripheral blood. The subgroup analysis showed that patients with higher disease severity had higher levels of Th22 [mild: WMD = 1.33, 95% CI (1.24, 1.41), p < 0.001; moderate: WMD = 1.41, 95% CI (1.36, 1.54), p < 0.001; severe: WMD = 3.46, 95% CI (3.34, 2.81), p < 0.001] and lower levels of Tregs [mild: WMD = -1.43, 95% CI (-1.75, -1.11), p < 0.001; moderate: WMD = -2.16, 95% CI (-2.46, -1.86), p < 0.001; severe: WMD = -2.96, 95% CI (-3.25, -2.67), p < 0.001] in peripheral blood compared to healthy controls.The random effect model of the meta-analysis showed patients with AD had an increased proportion of Th22 cells, Th17 cells, and IL-17, whereas a decreased proportion of Tregs was found in peripheral blood. The results demonstrated that Th22 cells, Th17 cells, IL-17, and Tregs may be involved in the pathogenic mechanisms of AD.