CXCL8 and irritable bowel syndrome: A total of 10 studies investigated the effects of PPs on inflammatory markers in IBD (Table 1, Table 2 and Table 4), including faecal calprotectin, C-reactive protein (CRP), ESR, transforming growth factor beta (TGF-β), tumour necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), nuclear factor-kappa beta (NF-κB), (interleukin 8) IL-8, growth regulated oncogene (GRO), granulocyte macrophage colony-stimulating factor (GM-CSF), platelet level, and mean platelet volume.