Correlation of ex vivo cytokine secretion profiles with scoring indices in ulcerative colitis.

BACKGROUND: In ulcerative colitis, the complexity of mucosal cytokine secretion profiles and how they correlate with endoscopic and clinical scores is still unclear. METHODS: In this study, we collected fresh biopsies from UC patients to investigate which cytokines are produced in ex vivo culture conditions, a platform increasingly used for testing of novel drugs. Then, we correlated cytokine production with several scoring indices commonly used to assess the severity of the disease. RESULTS: Increased levels of IL-1ß, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, TNFα and IFNÉ£ were produced by biopsies of UC patients compared to non-IBD controls. Our results show a better correlation of cytokine levels with Mayo Endoscopic Subscore (MES) and Mayo score, than the more complex Ulcerative Colitis Endoscopic Index of Severity (UCEIS). Out of 10 measured cytokines, eight correlated with MES, six with Mayo score and only three with UCEIS, due to the partial increase in cytokine secretion observed in donors with UCEIS = 7-8. When we analysed individual subscores within the UCEIS, Vascular Network subscore showed a correlation similar to MES (7/10 cytokines), while Bleeding as well as Erosions and Ulcers subscores correlated with only 3/10 cytokines, similarly to the total UCEIS. CONCLUSIONS: Our findings suggest that choosing biopsies from donors with MES = 2-3 and UCEIS = 2-6 from areas with no bleeding and no superficial and/or deep ulcers could enable a deeper insight into the cytokine profile of the inflamed tissue and represent a better tool for studying potential therapeutic targets and evaluation of novel therapies.

Size-Dependent Segregation Controls Macrophage Phagocytosis of Antibody-Opsonized Targets.

Macrophages protect the body from damage and disease by targeting antibody-opsonized cells for phagocytosis. Though antibodies can be raised against antigens with diverse structures, shapes, and sizes, it is unclear why some are more effective at triggering immune responses than others. Here, we define an antigen height threshold that regulates phagocytosis of both engineered and cancer-specific antigens by macrophages. Using a reconstituted model of antibody-opsonized target cells, we find that phagocytosis is dramatically impaired for antigens that position antibodies >10 nm from the target surface. Decreasing antigen height drives segregation of antibody-bound Fc receptors from the inhibitory phosphatase CD45 in an integrin-independent manner, triggering Fc receptor phosphorylation and promoting phagocytosis. Our work shows that close contact between macrophage and target is a requirement for efficient phagocytosis, suggesting that therapeutic antibodies should target short antigens in order to trigger Fc receptor activation through size-dependent physical segregation.