Humoral immune response
The aim of this research line is to develop new diagnostic and preferentially also therapeutic options to further prevent and/or treat allo- or autoimmunization against blood cells. We are studying both the antigens, which are the targets of the immune response, and the humoral immune response (outlined below) that leads to cell destruction.
Project leader: Gestur Vidarsson PhD
Humoral immune response
In most immune-mediated blood cell diseases and in all fetal/neonatal alloimmune cytopenias the destruction of blood cells is mediated by antibodies. We are therefore investigating both 1) the B cells, 2) the characteristics of these antibodies and 3) the interaction of antibodies with the FcRn, the receptor responsible for placental transport.
In a previously developed culture method in which B cells are stimulated to Immunoglobulin (Ig) production at the single cell level, we found that in hyper immune anti-D donors the majority of antigen-specific memory cells resides in the IgM-positive B cells. Upon antigen challenge the number of IgG-positive cells increased, whereas the IgM positive cells remained stable. We have now shown that these IgM memory cells are mostly CD27-negative, but harbor both mutations in the BCL-6 gene and in the variable regions of the VH and VL genes, proving that these cells are true memory cells. In analogy with recent studies in mice, we postulate that the IgM memory cells will not class-switch in the presence of IgG in the serum, but can replenish the memory pool once the titer has dropped and in case of infectious agents the antigenic make-up of the pathogen might have changed.
Antibodies and their receptors
By analyzing the Fc-glycosylation of the IgG1 alloantibodies formed during pregnancy against antigens of the fetus (Human Platelet Antigen-1 or RhD) using mass spectrometry, we have found markedly decreased levels of core-fucosylation and increased levels of galactosylation and sialylation. Because IgG glycosylation, in particular IgG Fc-core-fucosylation influences binding to FcγR, this translates into altered effector function that can have a profound effect on disease severity and prognosis. We have also found that these responses are also found that the proinflammatory status of patients can also influence clinical features in immune thrombocytopenia’s through C-reactive protein (CRP). This serum protein was increased in cord blood samples of fetal neonatal alloimmune thrombocytopenia affected neonates. In a murine model of idiopathic thrombocytopenic purpura it was demonstrated that CRP enhances the antibody mediated breakdown of platelets (Figure 1).
Human IgG3 displays the strongest effector functions of all human IgG subclasses but has a short half-life, suggesting FcRn-mediated IgG salvage to be defective for IgG3. We have previously observed that human IgG1 inhibited FcRn-mediated transport of IgG3 at the level of receptor binding. This inhibition was due to a single amino acid difference at position 435, where IgG3 has an arginine instead of the histidine. Importantly we showed that the half lives of natural H435-containing IgG3 allotypes in humans are comparable to IgG1. This H435-IgG3 also proved better suited for protection against pneumococcal challenge in mice, demonstrating that H435-IgG3 is a formidable candidate for monoclonal antibody therapies in patients.
- Kapur R, Heitink-Pollé KM, Porcelijn L, Bentlage AE, Bruin MC, Visser R, Roos D, Schasfoort RB, de Haas M, van der Schoot CE, Vidarsson G. C-reactive protein enhances IgG-mediated phagocyte responses and thrombocytopenia. Blood 2015; 125(11):1793-802.
- Vidarsson G, Dekkers G, Rispens T. IgG subclasses and allotypes: from structure to effector functions. Front Immunol 2014;5:520.
- Della Valle L, Dohmen SE, Verhagen OJ, Berkowska MA, Vidarsson G, van der Schoot CE. The Majority of Human Memory B Cells Recognizing RhD and Tetanus Resides in IgM+ B Cells. J Immunol 2014; 193(3):1071-9.
- Kapur R, Della Valle L, Sonneveld M, Hipgrave Ederveen A, Visser R, Ligthart P, de Haas M, Wuhrer M, van der Schoot CE, Vidarsson G. Low anti-RhD IgG-Fc-fucosylation in pregnancy: a new variable predicting severity in haemolytic disease of the fetus and newborn. Br J Haematol 2014; 166(6):936-45.
- van Bladel ER**, Laarhoven AG**, van der Heijden LB, Heitink-Pollé KM, Porcelijn L, van der Schoot CE, de Haas M, Roest M, Vidarsson G*, de Groot PG*, Bruin MC*. (*/** Equal contributions). Functional platelet defects in children with severe chronic ITP as tested with two novel assays applicable for low platelet counts. Blood 2014; 123(10):1556-63.
- Kapur R, Kustiawan I,Vestrheim A, Koeleman CAM, Porcelijn L, Jackson D, Kumpel B, Deelder AM, Blank D, Skogen B, Killie MK, Michaelsen TE, de Haas M, Rispens T, van der Schoot CE, Wuhrer M and Vidarsson G. A prominent lack of IgG1 Fc-fucosylation of platelet-alloantibodies in pregnancy. (Plenary paper) Blood 2014; 123(4):471-80.
- Stapleton NM, Andersen JT, Stemerding AM, Bjarnarson SP, Verheul RC, Gerritsen J, Zhao Y, Kleijer M, Sandlie I, de Haas M, Jonsdottir I, van der Schoot CE, Vidarsson G. Competition for FcRn-mediated transport gives rise to short half-life of human IgG3 and offers therapeutic potential. Nature Commun 2011; 2:599.