S100A9 and inflammatory bowel disease: Among 477 identified human proteins, 21 proteins significantly increased in IBD were involved in immune response and proteolysis, such as the S100 family protein (S100A8, S100A9, S100A12), myeloperoxidase (MPO), immunoglobulin (IGHG1, IGKC), cathepsin G (CTSG), azurocidin (AZU1), and leukocyte protease inhibitor (SERPINB1, SERPINA3) (Fig. S6).