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* = Presenting author

P010 Infliximab skews macrophages towards an IL10-high/IL12p40-low phenotype in an Fc region dependent manner

F. Bloemendaal*1, M. Wildenberg1, A. Levin1, P. Koelink1, A.C. Vos2, G. D’Haens1, G. van den Brink1

1Academic Medical Centre, Gastroenterology, Amsterdam, Netherlands, 2Leiden University Medical Centre, Gastroenterology, Leiden, Netherlands

Background

Infliximab has been shown to induce mucosal healing in a considerable proportion of Crohn’s patients, whereas certolizumab shows a very low healing rate. These observations suggest that features other than TNF neutralisation contribute to the therapeutic potency of anti-TNF antibodies in IBD patients. We have previously shown that infliximab induces CD206+ macrophages in vitro in an Fc region dependent manner. In this study, we further studied the specific effect of the Fc region on macrophage skewing by comparison of infliximab and certolizumab.

Methods

We cultured monocytes from healthy donors with IFN-γ and LPS in the presence of infliximab, certolizumab, and/or complexed IgG1 and measured IL-10, p40, IL23, and IL-12p70 by ELISA. We co-cultured monocytes with CD4+CD45RO+ memory T-cells and examined Th1 and Th17 skewing in-vitro with flow cytometry by staining for intracellular cytokines.

Results

We previously showed that infliximab induces CD206+ regulatory macrophages with immunosuppressive capacity in a mixed lymphocyte model system. We now simplified this model by generating monocytes in the presence of IFN-γ and either infliximab or certolizumab. Indeed infliximab induced macrophages showed significantly decreased immunogenicity. Cytokine analysis showed that infliximab treated monocytes produced increased amounts of IL-10 and decreased levels of IL12p40 and IL-23 compared with certolizumab treated monocytes. T-cells cultured in the presence of these infliximab treated macrophages expressed lower levels of IFN-γ and IL-17. Addition of complexed nonspecific IgG1 to the certolizumab treated cultures resulted in a phenotype comparable to infliximab treatment, emphasising the role of Fc receptor signalling. Interestingly, skewing to the IL10-high/IL12p40-low phenotype could be achieved both in naïve monocytes and in macrophages already skewed towards a pro-inflammatory M1 type, indicating high cellular plasticity.

Conclusion

These data show that the Fc region of infliximab contributes to the induction of a regulatory macrophage by skewing monocytes towards an IL10-high/IL12p40-low phenotype, resulting in decreased Th1 and Th17 responses.