The Regulation of Micro-Organisms’ Extra-Cellular Polysaccharides on Immunity: A Meta-Analysis

Extra-cellular polysaccharides (EPSs) have excellent immunomodulatory functions. In order to further promote their application, we studied the ability of extra-cellular polysaccharides from different sources to regulate immunity. We studied the association of extra-cellular polysaccharides with immune factors (Interleukin (IL-2, IL-4, IL-10), Interferon γ (IFN-γ), tumor necrosis factor-α (TNF-α), Immunoglobulin A (IgA), and Immunoglobulin G (IgG)) and different concentrations of EPSs and interfering media on experimental results by using a forest plot under fixed-effect or random-effects models. Through Google, PubMed, Embase, ScienceDirect, and Medline, from 2000 to 2021, 12 articles were included. We found that exopolysaccharides (from bacteria or fungi) could significantly increase the immune index of spleen and thymus, spleen index (SMD: 2.11, ‘95%CI: [1.15, 3.08]’; p < 0.01), and thymus index (SMD: 1.62, ‘95%CI: [0.93, 2.32]’; p = 0.01 < 0.05). In addition, exopolysaccharides had a significant effect on TNF-α (SMD: 0.94, ‘95%CI: [0.29, 1.59]’; p = 0.01 < 0.05). For IL-4 (SMD: 0.49, ‘95%CI: [0.01, 0.98]’; p = 0.046 < 0.05), extra-cellular polysaccharides had a statistically significant effect on immunity. Although the data of other immune factors were not ideal, the comprehensive analysis showed that exopolysaccharides also had an effect on the release of these five immune factors. In the sub-group analysis, different concentrations of EPSs affected the results of experiments on the spleen and thymus, and the CY intervention had a relatively significant effect on immune regulation. Taken together, our study highlighted that EPSs have a significant impact on immune regulation.