C1QA and staphylococcus aureus infection: Based on the functional enrich analysis of the LC-MS/MS results, the serum levels of C1QA and C1QB were significantly increased in patients with ISS compared with controls, and the crucial enriched terms were related to immunity and inflammation, including acute inflammatory response, Staphylococcus aureus infection, complement activation, humoral immune response, IgM immunoglobulin complex, etc. Therefore, we assumed that inflammation and immune-related factors such as C1QA and C1qB may play an essential role in the potential pathogenesis of ISS.