Diagnosis and treatment of autoimmune diseases

A method of analyzing a biological sample, the method comprising:

• (i) providing a biological sample of a human subject suspected of having an autoimmune disease;
• (ii) measuring a level of cleaved high molecular weight kininogen (HMWK) in the biological sample,
• (iii) identifying the human subject having a level of cleaved HMWK in the biological sample that is elevated compared to a control sample as having the autoimmune disease, and
• (iv) administering to the human subject identified in step (iii) a plasma kallikrein (pKal) inhibitor, an anti-inflammatory agent, or a combination thereof;
• wherein the biological sample and the control sample are a serum sample, a blood sample, or a plasma sample;
• wherein the autoimmune disease is selected from the group consisting of:
• inflammatory bowel disease, rheumatoid arthritis, Crohn's disease, and ulcerative colitis;
• and
• wherein the level of cleaved HMWK is measured by an assay that involves a binding agent specific to cleaved HMWK.