Short-chain fatty acids (SCFAs) produced by bacteria were decreased, which led to a reduction in the immune checkpoint molecules and an imbalance of T cells (Treg/Th17) and B cells (IL-10/IL-17 producing B cells), which provides a proinflammation microenvironment in SS, and induces chronic local gut mucosal inflammation, which causes systemic chronic non-specific inflammation [84,85,93]. Here, IL17A is linked to synovial sarcoma.