Transient leukopenia and anaphylatoxin production during granulocyte apheresis as treatment for ulcerative colitis

It is well known that transient leukopenia due to activation of the alternative pathway of the complement system accompanies hemodialysis when cellulose acetate dialyzers are used. However, it has not been evaluated whether leukopenia also occurs during granulocyte apheresis (GCAP) as treatment for ulcerative colitis, in which an extracorporeal column is filled with cellulose acetate beads in order to remove circulating leukocytes. The aim of the present study was to evaluate whether transient leukopenia and activation of the alternative pathway of the complement system were observed during GCAP. In 8 patients undergoing GCAP weekly for 10 weeks, circulating leukocyte counts and plasma concentrations of C3a, a product of the activated alternative pathway of the complement system, were determined. GCAP elicited a rapid decline in the number of circulating leukocytes to 61.8 +/- 13.8% of the baseline value after 15 minutes of GCAP (P < 0.02). Thereafter, the number of circulating leukocytes returned to approximately baseline after 60 minutes. The baseline plasma C3a concentration was 123 +/- 61 ng/mL, and a significant increase to 425 +/- 123 ng/mL was observed after 15 minutes of GCAP (P < 0.02). The plasma C3a concentration reached 417 +/- 96 ng/mL after 60 minutes (P < 0.02). It thus follows that GCAP activates the alternative pathway of the complement system, resulting in anaphylatoxin production.