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Glycobiology Mar 2020IgG glycosylation is currently at the forefront of both immunology and glycobiology, likely due in part to the widespread and growing use of antibodies as drugs. For... (Review)
Review
IgG glycosylation is currently at the forefront of both immunology and glycobiology, likely due in part to the widespread and growing use of antibodies as drugs. For over four decades, it has been recognized that the conserved N-linked glycan on asparagine 297 found within the second Ig domain of the heavy chain (CH2) that helps to comprise Fc region of IgG plays a special role in IgG structure and function. Changes in galactosylation, fucosylation and sialylation are now well-established factors, which drive differential IgG function, ranging from inhibitory/anti-inflammatory to activating complement and promoting antibody-dependent cellular cytotoxicity. Thus, if we are to truly understand how to design and deploy antibody-based drugs with maximal efficacy and evaluate proper vaccine responses from a protective and functional perspective, a deep understanding of IgG glycosylation is essential. This article is intended to provide a comprehensive review of the IgG glycosylation field and the impact glycans have on IgG function, beginning with the earliest findings over 40 years ago, in order to provide a robust foundation for moving forward.
Topics: Animals; Glycosylation; History, 20th Century; History, 21st Century; Humans; Immunoglobulin G; Polysaccharides
PubMed: 31504525
DOI: 10.1093/glycob/cwz065 -
Journal of Hematology & Oncology May 2020The intact antibody of human immunoglobulin (IgG) is composed of the fragment for antigen binding (Fab) and the crystallizable fragment (Fc) for binding of Fcγ... (Review)
Review
The intact antibody of human immunoglobulin (IgG) is composed of the fragment for antigen binding (Fab) and the crystallizable fragment (Fc) for binding of Fcγ receptors. Among the four subclasses of human IgG (IgG1, IgG2, IgG3, IgG4), which differ in their constant regions, particularly in their hinges and CH2 domains, IgG1 has the highest FcγR-binding affinity, followed by IgG3, IgG2, and IgG4. As a result, different subclasses have different effector functions such as antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). Fcγ receptors include six subtypes (FcγRI, FcγRIIA, FcγRIIB, FcγRIIC, FcγRIIIA, FcγRIIIB) which differ in cellular distribution, binding affinity to Fc, and the resulting biological activity. Therefore, when developing anti-tumor therapeutic antibodies, including single-targeted antibodies, bi-specific antibodies (BsAbs), and antibody-drug conjugates (ADCs), many factors, such as target biology, cellular distribution of the targets, the environments of particular tumor types, as well as the proposed mechanism of action (MOA), must be taken into consideration. This review outlines fundamental strategies that are required to select IgG subclasses in developing anti-tumor therapeutic antibodies.
Topics: Animals; Antineoplastic Agents, Immunological; Drug Development; Drug Discovery; Humans; Immunoglobulin G; Neoplasms; Receptors, IgG
PubMed: 32370812
DOI: 10.1186/s13045-020-00876-4 -
Clinical & Developmental Immunology 2012Placental transfer of maternal IgG antibodies to the fetus is an important mechanism that provides protection to the infant while his/her humoral response is... (Review)
Review
Placental transfer of maternal IgG antibodies to the fetus is an important mechanism that provides protection to the infant while his/her humoral response is inefficient. IgG is the only antibody class that significantly crosses the human placenta. This crossing is mediated by FcRn expressed on syncytiotrophoblast cells. There is evidence that IgG transfer depends on the following: (i) maternal levels of total IgG and specific antibodies, (ii) gestational age, (iii) placental integrity, (iv) IgG subclass, and (v) nature of antigen, being more intense for thymus-dependent ones. These features represent the basis for maternal immunization strategies aimed at protecting newborns against neonatal and infantile infectious diseases. In some situations, such as mothers with primary immunodeficiencies, exogenous IgG acquired by intravenous immunoglobulin therapy crosses the placenta in similar patterns to endogenous immunoglobulins and may also protect the offspring from infections in early life. Inversely, harmful autoantibodies may cross the placenta and cause transitory autoimmune disease in the neonate.
Topics: Female; Humans; Immunity, Maternally-Acquired; Immunoglobulin G; Immunologic Deficiency Syndromes; Infant, Newborn; Models, Immunological; Placenta; Pregnancy; Pregnancy Complications
PubMed: 22235228
DOI: 10.1155/2012/985646 -
MAbs 2012The disulfide bond structures established decades ago for immunoglobulins have been challenged by findings from extensive characterization of recombinant and human... (Review)
Review
The disulfide bond structures established decades ago for immunoglobulins have been challenged by findings from extensive characterization of recombinant and human monoclonal IgG antibodies. Non-classical disulfide bond structure was first identified in IgG4 and later in IgG2 antibodies. Although, cysteine residues should be in the disulfide bonded states, free sulfhydryls have been detected in all subclasses of IgG antibodies. In addition, disulfide bonds are susceptible to chemical modifications, which can further generate structural variants such as IgG antibodies with trisulfide bond or thioether linkages. Trisulfide bond formation has also been observed for IgG of all subclasses. Degradation of disulfide bond through β-elimination generates free sulfhydryls disulfide and dehydroalanine. Further reaction between free sulfhydryl and dehydroalanine leads to the formation of a non-reducible cross-linked species. Hydrolysis of the dehydroalanine residue contributes substantially to antibody hinge region fragmentation. The effect of these disulfide bond variations on antibody structure, stability and biological function are discussed in this review.
Topics: Antibodies, Monoclonal; Disulfides; Humans; Immunoglobulin G; Protein Isoforms; Recombinant Proteins
PubMed: 22327427
DOI: 10.4161/mabs.4.1.18347 -
Biotechnology and Bioengineering Mar 2015Fed-batch Chinese hamster ovary (CHO) cell culture is the most commonly used process for IgG production in the biopharmaceutical industry. Amino acid and glucose...
Fed-batch Chinese hamster ovary (CHO) cell culture is the most commonly used process for IgG production in the biopharmaceutical industry. Amino acid and glucose consumption, cell growth, metabolism, antibody titer, and N-glycosylation patterns are always the major concerns during upstream process optimization, especially media optimization. Gaining knowledge on their interrelations could provide insight for obtaining higher immunoglobulin G (IgG) titer and better controlling glycosylation-related product quality. In this work, different fed-batch processes with two chemically defined proprietary media and feeds were studied using two IgG-producing cell lines. Our results indicate that the balance of glucose and amino acid concentration in the culture is important for cell growth, IgG titer and N-glycosylation. Accordingly, the ideal fate of glucose and amino acids in the culture could be mainly towards energy and recombinant product, respectively. Accumulation of by-products such as NH4(+) and lactate as a consequence of unbalanced nutrient supply to cell activities inhibits cell growth. The levels of Leu and Arg in the culture, which relate to cell growth and IgG productivity, need to be well controlled. Amino acids with the highest consumption rates correlate with the most abundant amino acids present in the produced IgG, and thus require sufficient availability during culture. Case-by-case analysis is necessary for understanding the effect of media and process optimization on glycosylation. We found that in certain cases the presence of Man5 glycan can be linked to limitation of UDP-GlcNAc biosynthesis as a result of insufficient extracellular Gln. However, under different culture conditions, high Man5 levels can also result from low α-1,3-mannosyl-glycoprotein 2-β-N-acetylglucosaminyltransferase (GnTI) and UDP-GlcNAc transporter activities, which may be attributed to high level of NH4+ in the cell culture. Furthermore, galactosylation of the mAb Fc glycans was found to be limited by UDP-Gal biosynthesis, which was observed to be both cell line and cultivation condition-dependent. Extracellular glucose and glutamine concentrations and uptake rates were positively correlated with intracellular UDP-Gal availability. All these findings are important for optimization of fed-batch culture for improving IgG production and directing glycosylation quality.
Topics: Amino Acids; Animals; Batch Cell Culture Techniques; Bioreactors; CHO Cells; Cricetinae; Cricetulus; Glucose; Glycosylation; Immunoglobulin G; Metabolic Networks and Pathways; Polysaccharides
PubMed: 25220616
DOI: 10.1002/bit.25450 -
Journal of Proteome Research May 2021Immunoglobulin G (IgG) glycosylation is studied in biological samples to develop clinical markers for precision medicine, for example, in autoimmune diseases and...
Immunoglobulin G (IgG) glycosylation is studied in biological samples to develop clinical markers for precision medicine, for example, in autoimmune diseases and oncology. Inappropriate storage of proteins, lipids, or metabolites can lead to degradation or modification of biomolecular features, which can have a strong negative impact on accuracy and precision of clinical omics studies. Regarding the preservation of IgG glycosylation, the range of appropriate storage conditions and time frame is understudied. Therefore, we investigated the effect of storage on IgG Fc N-glycosylation in the commonly analyzed biofluids, serum and plasma. Short-term storage and accelerated storage stability were tested by incubating samples from three healthy donors under stress conditions of up to 50 °C for 2 weeks using -80 °C for 2 weeks as the reference condition. All tested IgG glycosylation features-sialylation, galactosylation, bisection, and fucosylation-remained unchanged up to room temperature as well as during multiple freeze-thaw cycles and exposure to light. Only when subjected to 37 °C or 50 °C for 2 weeks, galactosylation and sialylation subtly changed. Therefore, clinical IgG glycosylation analysis does not rely as heavily on mild serum and plasma storage conditions and timely analysis as many other omics analyses.
Topics: Biomarkers; Glycosylation; Immunoglobulin Fc Fragments; Immunoglobulin G
PubMed: 33909442
DOI: 10.1021/acs.jproteome.1c00148 -
The Journal of Biological Chemistry Mar 2001Immunoglobulin G (IgG) Fc receptors play a critical role in linking IgG antibody-mediated immune responses with cellular effector functions. A high resolution map of the...
High resolution mapping of the binding site on human IgG1 for Fc gamma RI, Fc gamma RII, Fc gamma RIII, and FcRn and design of IgG1 variants with improved binding to the Fc gamma R.
Immunoglobulin G (IgG) Fc receptors play a critical role in linking IgG antibody-mediated immune responses with cellular effector functions. A high resolution map of the binding site on human IgG1 for human Fc gamma RI, Fc gamma RIIA, Fc gamma RIIB, Fc gamma RIIIA, and FcRn receptors has been determined. A common set of IgG1 residues is involved in binding to all Fc gamma R; Fc gamma RII and Fc gamma RIII also utilize residues outside this common set. In addition to residues which, when altered, abrogated binding to one or more of the receptors, several residues were found that improved binding only to specific receptors or simultaneously improved binding to one type of receptor and reduced binding to another type. Select IgG1 variants with improved binding to Fc gamma RIIIA exhibited up to 100% enhancement in antibody-dependent cell cytotoxicity using human effector cells; these variants included changes at residues not found at the binding interface in the IgG/Fc gamma RIIIA co-crystal structure (Sondermann, P., Huber, R., Oosthuizen, V., and Jacob, U. (2000) Nature 406, 267-273). These engineered antibodies may have important implications for improving antibody therapeutic efficacy.
Topics: Antibody-Dependent Cell Cytotoxicity; Binding Sites; Crystallization; Glycosylation; Humans; Immunoglobulin G; Protein Engineering; Receptors, IgG; Structure-Activity Relationship
PubMed: 11096108
DOI: 10.1074/jbc.M009483200 -
Indian Journal of Dermatology,... 2016
Topics: Humans; Immunoglobulin G; Immunoglobulins, Intravenous; Male; Middle Aged; Scleromyxedema
PubMed: 26858056
DOI: 10.4103/0378-6323.174420 -
Frontiers in Immunology 2023Significant progress has been made in the elucidation of human antibody repertoires. Furthermore, non-canonical functions of antibodies have been identified that reach... (Review)
Review
Significant progress has been made in the elucidation of human antibody repertoires. Furthermore, non-canonical functions of antibodies have been identified that reach beyond classical functions linked to protection from pathogens. Polyclonal immunoglobulin preparations such as IVIG and SCIG represent the IgG repertoire of the donor population and will likely remain the cornerstone of antibody replacement therapy in immunodeficiencies. However, novel evidence suggests that pooled IgA might promote orthobiotic microbial colonization in gut dysbiosis linked to mucosal IgA immunodeficiency. Plasma-derived polyclonal IgG and IgA exhibit immunoregulatory effects by a diversity of different mechanisms, which have inspired the development of novel drugs. Here we highlight recent insights into IgG and IgA repertoires and discuss potential implications for polyclonal immunoglobulin therapy and inspired drugs.
Topics: Humans; Immunoglobulins, Intravenous; Immunoglobulin G; Antibody Diversity; Immunologic Deficiency Syndromes; Immunization, Passive; Immunoglobulin A
PubMed: 37063852
DOI: 10.3389/fimmu.2023.1166821 -
Journal of Animal Science Aug 2020Immunoglobulins (Ig) are essential components in the colostrum of bovine species that enable passive immunization of newborn calves. Concentrations of fat and protein...
Immunoglobulins (Ig) are essential components in the colostrum of bovine species that enable passive immunization of newborn calves. Concentrations of fat and protein are greater in colostrum compared with mature milk and represent a vital source of energy and nutrients. Colostral IgG was shown to vary between individual dairy cows, but comparative data on different breeds and performance levels are scarce. The objective of the present field study was to investigate the contents of total IgG, fat, protein, and lactose in colostrum in different Swiss and German dairy and dual-purpose breeds. We collected colostrum samples of 458 cows of 13 different breeds (dairy breeds: Brown Swiss, Swiss and German Holstein Friesian, and New Zealand Holstein; dual-purpose breeds: German Fleckvieh, Holstein Friesian × Montbéliarde, Montbéliarde, Murnau-Werdenfels, Original Braunvieh, Pinzgauer, Rhetic Gray, and Simmental; and beef-type crossbred: Charolais × Holstein Friesian). Colostrum samples were obtained between 5 and 900 min after calving and analyzed for total IgG, fat protein, and lactose contents. Immunoglobulin G concentrations varied between 12.7 and 204.0 mg/mL. No effect of breeding purpose (i.e., dairy or dual-purpose) nor of previous lactation yield on IgG content was observed. However, milking of cows for the first time later than 12 h after parturition resulted in lower colostrum IgG concentrations compared with colostrum harvest within 9 h after calving (P < 0.05). Multiparous cows had a higher colostral IgG concentration than primiparous cows (P < 0.0001). Overall, concentrations of IgG and other constituents in colostrum varied widely in the different cattle breeds. High-yielding dairy cows did not have poorer colostrum quality compared with lower-yielding animals or beef and dual-purpose breeds, which suggests an individually different transfer of circulating IgG into colostrum.
Topics: Animals; Cattle; Colostrum; Female; Immunoglobulin G; Lactation; Milk; Pregnancy
PubMed: 32697841
DOI: 10.1093/jas/skaa237