Evaluation of serum levels of IL-6, IL-10, and TNIF-α in alopecia areata patients: A systematic review and meta-analysis

Background: The role of pro and anti-inflammatory cytokines in autoimmune and inflammatory disorders has always been discussed; several studies have assayed serum levels of Interleukin-6 (IL-6), Tumor Necrosis Factor-alpha (TNF-alpha), and Interleukin-10 (IL-10) in alopecia areata (AA) patients. Determining the cytokine profile of AA patients will help us understand the role of the immune system in the pathogenesis of AA. Due to a lack of comprehensive studies in this regard, we have performed this meta-analysis to evaluate previously mentioned cytokines in AA patients. Method: We explored PubMed, Scopus, web of science, and ScienceDirect databases for research without a limited start date until May 2021. A number of 1098 studies were found in the initial database search and reference lists of relevant studies; 16 studies were finally included in the meta-analysis. Differences in the levels of IL-6, TNF-alpha, and IL-10 in sera of controls and patients were pooled as standardized mean differences. A random-effects model was used in this study. Begg's and Egger's tests were carried out to investigate publication bias. Results: 16 studies were included. This study found significantly elevated levels of IL-6 in AA patients compared to healthy subjects (SMD = 1.57, 95% CI 0.17 to 2.97). The levels of TNF-alpha were also significantly higher in the serum of AA patients (SMD = 2.05, 95% CI 0.98 to 3.13). Though IL-10 levels were lower in serum of AA patients, this difference was not significant (SMD = -0.22, 95% CI -0.95 to 0.50). Conclusion: According to the crucial role of cytokines in autoimmunity, alternation in the serum levels cytokines in AA patients was not unexpected; our study shows that cytokines might have an essential role in the pathogenesis of AA, though further studies are needed to clarify the exact role of cytokines in the emergence and persistence of AA.