Thesis Myrthe Sonneveld

On 22 September 2017 (14:00 hrs) Myrthe Sonneveld defended her thesis 'IgG-Fc-glycosylation in immune-mediated cytopenias' at the University of Amsterdam.

Promotores: Prof CE van der Schoot MD PhD and prof M Wuhrer PhD

Copromotor: G Vidarsson PhD

Venue: Agnietenkapel, Unversity of Amsterdam

Summary

Antibody Fc-glycosylation affects allo- and autoimmunity towards blood cells. Low Fc-fucosylation increases IgG-binding affinity to FcγRIIIa/b, thereby contributing to enhanced cell breakdown and hence, a worse clinical outcome. In this thesis we contribute to the development of new diagnostic assays to predict the severity of alloantibody derived blood diseases like haemolytic disease of the fetus or newborn (HDFN) and fetal or neonatal alloimmune thrombocytopenia (FNAIT) using Fc-glycosylation profiles. We found Fc-fucosylation to be the most important in predicting clinical outcome, followed by galactosylation and sialylation. Next to this, Fc-glycosylation patterns of autoantibody derived diseases like autoimmune haemolytic anemia (AIHA) and immune thrombocytopenia (ITP) were viewed. We found that total IgG1 from patients with RBC-bound antibodies showed significantly decreased galactosylation and sialylation levels compared to healthy controls, similar to what previously has been shown for other autoimmune diseases, but no changes for antigen-specific IgG Fc-glycosylation. We found that antigen-specific antibodies against alloantigens and enveloped viral antibodies show significantly lowered Fc-fucosylation, in contrast to autoantigens, viral antibodies derived after vaccination or non-enveloped viral antibodies which show normal high-level of Fc-fucosylation. This discrepancy could be explained by the immune system reacting differently in allo- and autoimmune diseases, where alloantigens are recognized as foreign membrane antigens in alloimmune diseases, inducing a non-fucosylation immune response.

Chapters

Chapter 1
General Introduction and scope of the thesis

Chapter 2
Glycosylation pattern of anti-platelet IgG is stable during pregnancy and predicts clinical outcome in alloimmune thrombocytopenia, abstract

Chapter 3
Low anti-RhD IgG-Fc-fucosylation in pregnancy: a new variable predicting severity in hemolytic disease of the fetus and newborn

Chapter 4
Antigen specificity determines anti-red blood cell IgG-Fc alloantibody glycosylation and thereby severity of hemolytic disease of the fetus and newborn, abstract

Chapter 5
IgG1 and IgG3 have similar glycosylation levels in immune responses

Chapter 6
Patients with IgG1-anti-red blood cell autoantibodies show aberrant Fc-glycosylation, abstract

Chapter 7
Serum IgG glycome composition in pediatric immune thrombocytopenia

Chapter 8
The origin of afucosylated IgG responses

Chapter 9
General Discussion