W1123 Adsorptive Depletion of Circulating α4 Integrin Hi and Cx 3Crl Hi Expressing Proinflammatory Monocytes in Patients with Active Ulcerative Colitis

Abstract

BACKGROUND AND AIM: Circulating monocytes exist as two main functionally distinct phenotypes, the CD14hiCD16“classical” phenotype and the CD14+CD16+ “proinflammatory” phenotype for releasing large amounts of tumour necrosis factor (TNF)-α. Further, the CD14+CD16+ phenotype is elevated by up to 2 fold (or more) in patients with inflammatory bowel disease (IBD) and is suspected to have a major role in the immunopathogenesis of IBD as this phenotype is readily recruited to inflammatory as well as to non-inflammatory mucosal tissues where they differentiate into cytokine producing resident macrophages or dendritic cells. Accordingly, selectively depletion of CD14+CD16+ monocytes should be a major research objective.METHODS: Seven corticosteroid naive patients with active ulcerative colitis (UC), Lichtiger's clinical activity index (CAI) = 8.7±1.3, and 7 healthy subjects as controls were included. In patients with UC, granulocyte/monocyte adsorption (GMA) was done with an Adacolumn that selectively adsorbs leucocytes of the myeloid lineage. Peripheral blood from all subjects at baseline and from patients immediately after the first GMA session was processed. Isolated monocytes were subjected to extensive fluorescenceactivated cell sorter (FACS) analyses. RESULTS: The 7 patients with UC achieved clinical remission (CAI≤4) after 5-10 GMA sessions. GMA was associated with a striking fall in the ratio (%) of CD14+CD16+/CD14hiCD16monocytes, from 10.0±1.4 to 3.0±0.9 (P<0.05), indicating selective depletion of CD14+CD16+ monocytes. Further, FACS analyses revealed that the expressions of the adhesion molecules α4 integrin, 374.8±26.1 mean fluorescence intensity (MFI) and CX3CR1, 49.5±4.6MFI were significantly (P<0.05) high on CD14+CD16+ monocytes as compared to CD14hiCD16monocytes, 169.2±17.2 MFI and 33.2±3.6 MFI, respectively. Additionally, GMA increased the ratio of the “immature” CD14hiCD16-CCR2low monocytes from 3.74±0.62 MFI to 8.11±0.56 MFI (P<0.05), indicating that GMA was followed by an influx of immature monocytes from the bone marrow into the circulation. CONCLUSIONS: To our knowledge, this is the first report of detecting elevated levels of α4 integrin on the proinflammatory CD14+CD16+ monocytes as compared to the classical CD14hiCD16monocytes. A high level of α4 integrin on the CD14+CD16+ monocytes might promote extravasation of these myeloid cells to the mucosa as significant sources of TNFα. GMA was very effective in depleting the CD14+CD16+ monocytes and at the same time, it was associated with an increase in CD14hiCD16-CCR2low monocytes. These data should contribute to a better understanding of immune pathology in patients with IBD.