Tumor necrosis factor-α-secreting CD16+ antigen presenting cells are effectively removed by granulocytapheresis in ulcerative colitis patients.

BACKGROUND AND AIM: In human blood, two main subsets of antigen-presenting-cells (APCs) have been described: plasmocytoid dendritic cells (pDC) and myeloid dendritic cells (mDC) which are further subdivided in CD11c-mDC and CD16-mDC DC. In ulcerative colitis patients (UC) peripheral blood APCs express significant levels of the activation and lack immature-tolerogeneic APCs. Adacolumn selective granulocytapheresis (GCAP) has been associated with clinical efficacy in patients with UC. In the present study we sought the effect of sequential GCAP procedures in peripheral blood APCs in patients with UC and the effect on soluble cytokines.

METHODS: We used multiparametric flow cytometry to quantify peripheral blood APCs and serum cytokines in 210 samples obtained from seven patients with steroid-dependent or steroid resistant UC undergoing GCAP treatment. Samples were drawn before, after 30 and 60 min of each session.

RESULTS: Each GCAP session resulted in a dramatic tenfold reduction of peripheral blood CD16-mDC (P < 0.01), pDC decreased twofold (P = 0.05) but CD11c-mDC remained unchanged. This depletion was reached after 30 min and maintained at 60 min. The depletion of CD16-mDC and monocytes was associated with a reduction of serum tumor necrosis factor levels and a raise in interleukin-10 levels, although no statistical difference was reached.

CONCLUSION: The effect of GCAP in peripheral blood APC consisted mainly on a significant depletion of tumor necrosis factor-α secreting CD16-mDC. This finding could suggest a potential mechanism of GCAP beneficial effect that must be confirmed in larger series.