Reduction of dendritic cells by granulocyte and monocyte adsorption apheresis in patients with ulcerative colitis.

The influence of the granulocyte/monocyte apheresis (GMCAP) on cell populations participating in mechanisms of tolerance, e.g. dendritic cells (DCs), is still not very clear. In a first step, we aimed to investigate changes in the DC population of patients suffering from ulcerative colitis (UC) (n = 13) compared to healthy subjects (n = 9). In a second step, we studied the changes in peripheral DCs in a small group of patients with active UC before and after Adacolumn apheresis (n = 7). For this purpose, plasmacytoid and myeloid DCs and their maturation markers CD40, CD80, and CD86 were measured using four-color flow cytometry in the peripheral blood. After apheresis, and in acute flare-ups, we identified a significantly lower number of lymphocytes, plasmacytoid, and myeloid DCs. In conclusion, the additional removal of peripheral DCs by GMCAP, which otherwise would contribute to the inflammatory process in the gut, may lead to a higher tolerogeneic status towards luminal antigens.