Activated platelets as a possible early marker to predict clinical efficacy of leukocytapheresis in severe ulcerative colitis patients

Background. Leukocytapheresis (LCAP) is an effective adjunct for patients with active ulcerative colitis (UC). Because LCAP may have the potential to remove and modulate not only leukocytes but also platelets, we evaluated the correlation between activated platelets and the therapeutic response to LCAP. Methods. Fourteen patients with severe UC received weekly LCAP for 5 consecutive weeks. Their average clinical activity index (CAI) and endoscopic index (EI) were 9.6 +/- 3.4 and 10.9 +/- 1.0, respectively. Their peripheral blood was sampled before and after every LCAP and stained with fluorescent antibodies to the activation-dependent surface antigens of platelets (CD63, CD62-P) prior to flow cytometry. Endoscopic evaluations were performed after the last LCAP. Results. Clinical remission (CAI < 4) was induced in 50% of the patients (7/14) after 5 weeks, and there were no significant differences observed in clinical background between the responder group (RG) and the nonresponder group (NG). In the RG, the populations of CD63(+) (P < 0.03) and CD62-P+ (P < 0.05) platelets were significantly decreased after the first LCAP, and their reduction ratio decreased gradually with repeated LCAP. A significant improvement of the EI score, especially mucosal damage, was achieved in RG (P < 0.04) but not in NG. Conclusions. These results indicate that the therapeutic responses to LCAP were reflected in modulations of population and/or platelet functions, especially after the first session. The decrease of such activated platelets immediately after the first LCAP may be an early marker for predicting the response in patients with severe UC.