To this day, immune thrombocytopenia (HT) remains a clinical diagnosis made by exclusion of other causes for thrombocytopenia. Reliable detection of platelet autoantibodies would support the... Show moreTo this day, immune thrombocytopenia (HT) remains a clinical diagnosis made by exclusion of other causes for thrombocytopenia. Reliable detection of platelet autoantibodies would support the clinical diagnosis, but the lack of specificity and sensitivity of the available methods for platelet autoantibody testing limits their value in the diagnostic workup of thrombocytopenia. The introduction of methods for glycoprotein-specific autoantibody detection has improved the specificity of testing and is acceptable for ruling in ITP but not ruling it out as a diagnosis. The sensitivity of these assays varies widely, even between studies using comparable assays. A review of the relevant literature combined with our own laboratory's experience of testing large number of serum and platelet samples makes it clear that this variation can be explained by variations in the characteristics of the tests, including in the glycoprotein-specific monoclonal antibodies, the glycoproteins that are tested, the platelet numbers used in the assay and the cutoff levels for positive and negative results, as well as differences in the tested patient populations. In our opinion, further standardization and optimization of the direct autoantibody detection methods to increase sensitivity without compromising specificity seem possible but will still likely be insufficient to distinguish the often very weak specific autoantibody signals from background signals. Further developments of autoantibody detection methods will therefore be necessary to increase sensitivity to a level acceptable to provide laboratory confirmation of a diagnosis of ITP. (C) 2020 The Author(s). Published by Elsevier Inc. Show less
Glycosylation is the most abundant and complex protein modification, and can have a profound structural and functional effect on the conjugate. The oligosaccharide fraction is recognized to be... Show moreGlycosylation is the most abundant and complex protein modification, and can have a profound structural and functional effect on the conjugate. The oligosaccharide fraction is recognized to be involved in multiple biological processes, and to affect proteins physical properties, and has consequentially been labeled a critical quality attribute of biopharmaceuticals. Additionally, due to recent advances in analytical methods and analysis software, glycosylation is targeted in the search for disease biomarkers for early diagnosis and patient stratification. Biofluids such as saliva, serum or plasma are of great use in this regard, as they are easily accessible and can provide relevant glycosylation information. Thus, as the assessment of protein glycosylation is becoming a major element in clinical and biopharmaceutical research, this review aims to convey the current state of knowledge on the N-glycosylation of the major plasma glycoproteins alpha-1-acid glycoprotein, alpha-1-antitrypsin, alpha-1B-glycoprotein, alpha-2-HS-glycoprotein, alpha-2-macroglobulin, antithrombin-III, apolipoprotein B-100, apolipoprotein D, apolipoprotein F, beta-2-glycoprotein 1, ceruloplasmin, fibrinogen, immunoglobulin (Ig) A, IgG, IgM, haptoglobin, hemopexin, histidine-rich glycoprotein, kininogen-1, serotransferrin, vitronectin, and zinc-alpha-2-glycoprotein. In addition, the less abundant immunoglobulins D and E are included because of their major relevance in immunology and biopharmaceutical research. Where available, the glycosylation is described in a site-specific manner. In the discussion, we put the glycosylation of individual proteins into perspective and speculate how the individual proteins may contribute to a total plasma N-glycosylation profile determined at the released glycan level. Show less
Zauner, G.; Koeleman, C.A.M.; Deelder, A.M.; Wuhrer, M. 2012
Schistosomes are parasitic helminths that cause chronic infections in over 200 million people in tropical and sub-tropical areas around the world. Glycoproteins from the eggs of the parasite... Show moreSchistosomes are parasitic helminths that cause chronic infections in over 200 million people in tropical and sub-tropical areas around the world. Glycoproteins from the eggs of the parasite Schistosoma mansoni induce various immune responses in the human host, including T-cell modulation and granuloma formation. Three major, immunogenic egg glycoproteins have been identified; omega-1, IPSE/_1 and kappa-5. The studies in this thesis have unraveled structural and molecular details of the interaction between these three glycoproteins and innate immune cells of the host. Firstly, we have studied the structural details of the N-glycans expressed on these three glycoproteins. Most notably, omega-1 and IPSE/_1 carry diantennary N-glycans which mainly display Lewis X motifs, while kappa-5 expresses triantennary N-glycans with LDN motifs. Then, we have investigated the interaction of the egg glycoproteins with C-type lectin receptors on antigen-presenting immune cells. We show that specific glycan motifs on the egg glycoproteins determine differential binding to these lectin receptors. Finally, we have investigated functional effects of omega-1 and kappa-5. We show that the Th2-modulating capacity of omega-1 is dependent on both glycan-lectin interactions as well as its RNase activity. We found that kappa-5 contains granuloma-inducing properties, which are partly mediated by its LDN motifs. Show less
Schistosomiasis, also known as bilharzia, is a disease that still occurs in many parts of Africa, the Middle East and Southern America, mainly Brasil and the Caribbean. Schistosomiasis is, after... Show moreSchistosomiasis, also known as bilharzia, is a disease that still occurs in many parts of Africa, the Middle East and Southern America, mainly Brasil and the Caribbean. Schistosomiasis is, after malaria, the second most common parasitic infection. Currently 200 million people are infected with the worms that cause the disease. Schistosoma mansoni is the most common schistosome species that infects humans. The schistosome produces many different sugar structures (glycans) that are not made by humans. Central to this thesis are sugar structures with a __double fucose__. Such fucosylated glycans are mainly produced by the eggs, which play a major role in the disease schistosomiasis. The human immune defence system responds to these parasite glycans in several ways. High antibody responses have been measured against sugar structures with a __double fucose__ moiety and different types of immune cells interact with these glycan structures. Despite these immunological responses the human host is not able to clear the parasitic infection. Glycans are thought to play a role in the mechanisms that S. mansoni has developed to survive in the hostile environment of the human blood. In this thesis the structures of several glycans containing the __double fucose__ moiety have been characterised using different mass spectrometric techniques. Show less
