Fetal and neonatal alloimmune thrombocytopenia (FNAIT) can occur due to maternal IgG antibodies targeting platelet antigens, causing life-threatening bleeding in the neonate. However, the disease... Show moreFetal and neonatal alloimmune thrombocytopenia (FNAIT) can occur due to maternal IgG antibodies targeting platelet antigens, causing life-threatening bleeding in the neonate. However, the disease manifests itself in only a fraction of pregnancies, most commonly with anti-HPA-1a antibodies. We found that in particular, the core fucosylation in the IgG-Fc tail is highly variable in anti-HPA-1a IgG, which strongly influences the binding to leukocyte IgG-Fc receptors IIIa/b (FcγRIIIa/b). Currently, gold-standard IgG-glycoanalytics rely on complicated methods (e.g., mass spectrometry (MS)) that are not suited for diagnostic purposes. Our aim was to provide a simplified method to quantify the biological activity of IgG antibodies targeting cells. We developed a cellular surface plasmon resonance imaging (cSPRi) technique based on FcγRIII-binding to IgG-opsonized cells and compared the results with MS. The strength of platelet binding to FcγR was monitored under flow using both WT FcγRIIIa (sensitive to Fc glycosylation status) and mutant FcγRIIIa-N162A (insensitive to Fc glycosylation status). The quality of the anti-HPA-1a glycosylation was monitored as the ratio of binding signals from the WT versus FcγRIIIa-N162A, using glycoengineered recombinant anti-platelet HPA-1a as a standard. The method was validated with 143 plasma samples with anti-HPA-1a antibodies analyzed by MS with known clinical outcomes and tested for validation of the method. The ratio of patient signal from the WT versus FcγRIIIa-N162A correlated with the fucosylation of the HPA-1a antibodies measured by MS (r=-0.52). Significantly, FNAIT disease severity based on Buchanan bleeding score was similarly discriminated against by MS and cSPRi. In conclusion, the use of IgG receptors, in this case, FcγRIIIa, on SPR chips can yield quantitative and qualitative information on platelet-bound anti-HPA-1a antibodies. Using opsonized cells in this manner circumvents the need for purification of specific antibodies and laborious MS analysis to obtain qualitative antibody traits such as IgG fucosylation, for which no clinical test is currently available. Show less
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is the most common cause of thrombocytopenia in otherwise healthy newborns. During pregnancy, fetal blood cells enter the maternal circulation... Show moreFetal and neonatal alloimmune thrombocytopenia (FNAIT) is the most common cause of thrombocytopenia in otherwise healthy newborns. During pregnancy, fetal blood cells enter the maternal circulation and might result in alloimmunization, the maternal production of antigen-specific alloantibodies. Once these alloantibodies enter the fetal circulation, they can cause damage. Clinical presentation can vary from an asymptomatic thrombocytopenia or relatively harmless bruises and petechiae to severe life-threatening and invalidating intracranial hemorrhages (ICHs). Once alloimmunization is detected and diagnosed, subsequent pregnancies can be treated to prevent the recurrence of bleeding complications. Unfortunately, in absence of population-based screening, alloimmunization is virtually only known after an affected fetus or newborn. Affected infants that might have been prevented if only the alloimmunization was known and treated prior to the occurrence of bleeding complications. Implementation of population-based screening in order to prevent FNAIT needs to be a carefully weighed decision. The benefits of screening need to outweigh the potential harm. To guide careful consideration and decision-making, Wilson and Jungner (W&J) proposed and published ten screening criteria. With this thesis, important evidence is presented that can be used for the fulfillment of the W&J criteria. Show less
Foetal or neonatal thrombocytopenia results from alloimmunisation during pregnancy. Maternal alloantibodies can be formed following exposure to paternally derived human platelet antigens (HPAs) on... Show moreFoetal or neonatal thrombocytopenia results from alloimmunisation during pregnancy. Maternal alloantibodies can be formed following exposure to paternally derived human platelet antigens (HPAs) on foetal platelets, in case of incompatible HPA type. These alloantibodies are of the immunoglobulin G subclass and can therefore enter the foetal circulation through active placental transport mediated by the neonatal Fc-receptor. After entering the foetal circulation, these alloantibodies can cause destruction of foetal platelets and potentially damage other foetal cells containing the specific antigen. Subsequent clinical presentation in foetuses or neonates can vary widely, from an asymptomatic thrombocytopenia to a broad spectrum of bleeding complications. Most frequently encountered are minor skin haemorrhages, such as hematomas or petechiae, but also more devastating haemorrhages can occur. Of these, an intracranial haemorrhage is the most feared complication because of its high risk of life-long major neurological handicaps or perinatal death. (C) 2019 Elsevier Ltd. All rights reserved. Show less
This thesis describes new knowledge of FNAIT in preparation of a national wide screening program. It illustrates the prevalence of FNAIT among pregnant women and the risk of adverse outcome,... Show moreThis thesis describes new knowledge of FNAIT in preparation of a national wide screening program. It illustrates the prevalence of FNAIT among pregnant women and the risk of adverse outcome, outlines current management, evaluates risks of missing a diagnosis of FNAIT, studies the efficacy of a lower dose of immunoglobulins in preventing bleedingcomplications,shows the time of bleeding onset of fetal ICH during pregnancy and illustrates the longterm outcome of children with ICH. Show less
