Asthma is a chronic inflammatory condition characterized by T-helper (Th)2 polarization. In children, the prevalence of obesity is associated with an increased incidence of asthma. Notably, obesity is linked with Th1-mediated inflammation and has been identified as a major risk factor of asthma.
To investigate the impact of obesity on Th1 (tumour necrosis factor-α, interferon-γ, interleukin (IL)-6, IL-8) and Th2 (IL-4, IL-5, IL-10, IL-13) immune responses in children with asthma.
We searched the MEDLINE and grey literature electronic databases for eligible studies from inception up until April 2020. The quality of included studies and evidence were independently assessed by two reviewers. The random-effect model was used in this meta-analysis and outcomes were reported as standardized mean difference (SMD), 95% confidence interval (CI).
Overall, four studies comprising of 482 participants met the inclusion criteria. The meta-analysis showed an increased Th2-mediated immune response in lean asthmatics when compared to non-asthmatic controls (SMD: -1.15 [95% CI: -1.93, 0.36]; I 2 = 93%, p H < 0.00001). However, in obese asthmatics, there was polarization towards Th1 immune response when compared to lean asthmatics (SMD: -0.43 [95% CI: -0.79, -0.08]; I 2 = 88%, p H <0.00001).
This meta-analysis shows that there are differences in immune responses mediated by T-helper cells in lean and obese asthmatic children. Moreover, and not unique to asthma, obesity polarizes the immune response towards Th1 rather than the classical Th2. This could be an important aspect to understand to establish effective therapeutic targets for obese-asthmatic children.

Copyright © 2020. Published by Elsevier Inc.