Observation of Granulocyte Adsorption in Adacolumn® Cellulose Acetate Beads after Granulocytapheresis

: Adacolumn is a therapeutic mode for ulcerative colitis that achieves therapeutic efficacy through the adhesion of leukocytes to cellulose acetate beads. We used scanning electron microscopy and observed leukocyte adsorption on Adacolumn beads after granulocytapheresis/granulocyte and monocyte adsorption apheresis. We then compared results between two patients with a low and high C-reactive protein (CRP) levels to determine whether adhesion is affected by a difference in leukocyte activity depending on the level of inflammation. We found that the surface layers of the beads from both patients were covered by a clay-like layer, and spherical granulocytes were adsorbed here and there on top of it. In cross-section the adsorbed granulocytes were visible in the clay-like layer and the surface layer alike. The clay-like layer had a maximum thickness of approximately 12 μm in the low CRP patient and approximately 50 μm in the high CRP patient, so in the high CRP patient the clay-like adsorption layer was thicker. Taken together, adsorption onto beads is considered to involve an immunological mechanism. Our findings suggest that granulocytes contact and adhere to each other at the surface layer after adsorption, and that granulocyte-granulocyte adhesion is enhanced by a higher inflammatory response.