Effect of interleukin-6 on IgG antibody glycosylation
Final Report Abstract
Blocking of the interleukin-6 receptor (IL-6R) with the monoclonal antibody (Ab) Tocilizumab is a successful therapy to treat patients with IgG autoAb-induced rheumatoide arthritis (RA). However, the influence of IL-6 on the induction of pathogenic T cell-dependent IgG autoAbs is still unclear. The pathogenic potential of IgG Abs is regulated by their IgG subclass and Fc glycosylation pattern. Non(a)- galactosylated IgG autoAbs are associated with the severity of RA, whereas galactosylated and terminal sialylated IgG autoAbs are linked to lower-/anti-inflammatory conditions. We could show by doing immunization studies with different adjuvants that the kind of adjuvant determines the IgG Fc galactosylation and sialylation level in the germinal center reaction. More inflammatory adjuvants induced lower IgG Fc galactosylation and sialylation levels. In this project, the role of IL-6 on the determination of low IgG Fc sialylation levels should be investigated after immunization with the model protein antigen ovalbumin (Ova) plus complete Freund`sch adjuvant (enriched with further mycobacteria; Ova-enriched (e)CFA). Furthermore, different conditional, cell-specific knock-out mouse strains should be investigated to figure out, which of three known IL-6 signaling routes are responsible for the induction of anti-Ova IgG Abs with low galactosylation and sialylation levels. I) in the classical IL-6 cis-signaling route, IL-6 binds to membrane-bound IL-6R; subsequently, this complex interacts and activates the membrane-bound signaling subunit gp130 on the same cell. II) in the trans-signaling route, IL-6 binds to shedded soluble IL-6R. This soluble complex is then activating also cells that only express gp130. III) in the trans-presentation / cluster signaling route, IL-6 binds to membrane-bound IL-6R from the same cell to interact and activate gp130 on another cell. Further, the potential of monoclonal blocking Abs against the IL-6R to block the induction of IgG Abs with low sialylation levels should be investigated. The experiments with IL-6-deficient mice showed that IL-6 is a major factor for the determination of IgG Abs with low sialylation levels in the germinal center reaction - independent of the adjuvant. Furthermore, the studies showed an intermediate influence of IL-6 from CD11c+ dendritic cells and a strong influence of the IL-6R on B cells for the induction of anti-Ova IgG Abs with low sialylation levels. It is still unclear, whether with two signaling ways are coupled or not. Any IL-6 trans-signaling via the soluble IL-6R could be excluded. Currently, we are continuing this project by investigating in particular the role of the IL-6R on germinal center B cells for the induction/determination of anti-Ova IgG Abs with low galactosylation and sialylation levels with internal money of the University of Lübeck. Further, we could show that an ant-IL-6R blocking Ab induced comparable results to IL-6-deficient mice. Finally, we would like to mention that the SARS-CoV-2 pandemic had delay the experiments so that we could not complete all planed experiments. However, we currently continue the project to answer open questions.
Publications
- IgG Fc sialylation is regulated during the germinal center reaction upon immunization with different adjuvants. J Allergy Clin Immunol 2020; 146(3):652-666
Bartsch YC, Eschweiler S, Leliavski A, Lunding H, Wagt S, Petry J, Lilienthal G-M, Rahmöller J, de Haan N, Hölscher A, Erapaneedi R, Giannou AD, Aly L, Sato R, de Neef LA, Winkler A, Braumann D, Hobusch J, Kuhnigk K, Krémer V, Steinhaus M, Blanchard V, Gemoll T, Habermann J, Collin M, Salinas-Riesters G, Manz R, Korn T, Fukuyama H, Waisman A, Yogev N, Huber S, Rabe B, Rose-John S, Busch H, Berberich-Siebelt F, Hölscher C, Wuhrer M, anfd Ehlers M
(See online at https://doi.org/10.1016/j.jaci.2020.04.059)
