Reduced free protein S levels in patients with inflammatory bowel disease: prevalence, clinical relevance, and role of anti-protein S antibodies

Dig Dis Sci. 2001 Mar;46(3):637-43. doi: 10.1023/a:1005675921664.


We evaluated free plasma levels of protein S, a natural anticoagulant factor, the prevalence of anti-protein S antibodies, a possible cause of protein S deficiency, and their correlation with anti-phospholipid antibodies in 53 patients with inflammatory bowel disease (IBD) and 53 age- and sex-matched controls. Mean free plasma protein S levels (+/- SD) were significantly lower in IBD patients (0.98+/-0.32 IU/ml) than in controls (1.06+/-0.28 IU/ml) (P < 0.05); only one patient showed protein S deficiency. Specific antibodies to protein S were found in four IBD patients (7.5%) and in one control (1.9%) (P = NS). Five IBD patients (9.4%) and none of the controls showed anti-phospholipid antibodies (P < 0.06). No correlation was found between free protein S levels and anti-protein S antibodies or between anti-protein S and anti-phospholipid antibodies. In conclusion, free plasma protein S levels are slightly but significantly decreased in IBD patients. The prevalence of anti-protein S and antiphospholipid antibodies is increased in IBD patients. Anti-protein S antibodies do not appear to determine low protein S levels or to overlap with or belong to anti-phospholipid antibodies.

MeSH terms

  • Adult
  • Autoantibodies / blood*
  • Female
  • Humans
  • Immunoblotting
  • Inflammatory Bowel Diseases / blood*
  • Inflammatory Bowel Diseases / immunology*
  • Male
  • Phospholipids / immunology
  • Protein S / analysis*
  • Protein S / immunology*


  • Autoantibodies
  • Phospholipids
  • Protein S