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Fragment antigen-binding region

The fragment antigen-binding (Fab) region is the antigen-recognizing portion of an antibody molecule, comprising one complete light chain and the variable domain (V_H) plus the first constant domain (C_H1) of the heavy chain, which together form a monovalent binding unit with a molecular weight of approximately 50 kDa.^[1] This structure enables the Fab to specifically interact with epitopes on antigens through complementary interactions in its hypervariable complementarity-determining regions (CDRs), facilitating immune recognition without the effector functions associated with the antibody's Fc region.^[2] Discovered in 1958 by Rodney R. Porter through papain digestion of rabbit gamma-globulin, which yielded two identical Fab fragments capable of antigen binding and one crystallizable Fc fragment lacking such activity, the Fab's elucidation was pivotal in defining antibody architecture and earned Porter the 1972 Nobel Prize in Physiology or Medicine, shared with Gerald M. Edelman.^[3]^[1] In modern applications, isolated Fab fragments are engineered for therapeutic use, such as in monoclonal antibody-derived drugs like ranibizumab for macular degeneration, due to their reduced immunogenicity and ability to penetrate tissues more effectively than full antibodies.^[4] The Fab's modular design also underpins diagnostic tools and research reagents, where its antigen specificity is harnessed without Fc-mediated complications like complement activation.^[5]

Structure

Composition and Domains

The fragment antigen-binding (Fab) region consists of one complete light chain and the N-terminal half of one heavy chain, forming a heterodimeric unit that serves as the antigen-recognizing arm of an antibody molecule. The light chain, either of the kappa (κ) or lambda (λ) isotype, has a molecular weight of approximately 25 kDa and comprises a variable domain (VL) and a constant domain (CL).^[6] The heavy chain portion includes the variable domain (VH) and the first constant domain (CH1), also totaling about 25 kDa, with the two chains covalently linked by a disulfide bond between CL and CH1.^[1] This arrangement yields an overall Fab molecular weight of roughly 50 kDa.^[6] Structurally, the Fab features immunoglobulin folds in the form of beta-sandwich domains, each composed of two antiparallel β-sheets stabilized by an intra-domain disulfide bond. The variable domains, VL and VH, are located at the distal end and each contain three hypervariable loops known as complementarity-determining regions (CDRs)—CDR1, CDR2, and CDR3—flanked by four conserved framework regions that maintain the overall domain architecture.^[1] These CDRs contribute to the diversity and specificity of antigen binding, while the framework regions provide a scaffold for their positioning.^[6] In contrast, the CH1 domain, paired with CL, primarily stabilizes the Fab structure without direct involvement in antigen contact.^[1] The heterodimer assembles through non-covalent interactions, with the light chain associating with the heavy chain via hydrophobic contacts at the VL-VH interface and complementary interactions between CL and CH1.^[6] This modular domain organization allows the Fab to adopt an elbow-bent conformation, facilitating flexibility in antigen engagement. In the intact antibody, two identical Fab regions are joined to the Fc domain by the flexible hinge region, enabling bivalent interactions with antigens.^[1]

Antigen-Binding Site

The paratope is the antigen-binding surface located at the tip of the Fab fragment, primarily formed by the six complementarity-determining regions (CDRs)—three from the variable light chain (VL: CDR-L1, CDR-L2, CDR-L3) and three from the variable heavy chain (VH: CDR-H1, CDR-H2, CDR-H3)—which collectively create a binding pocket or groove complementary to the epitope on the antigen.^[7] These CDRs, also known as hypervariable loops, protrude from the beta-sheet framework of the VL and VH domains, positioning their diverse amino acid side chains to form the specific interaction interface.^[8] The structural diversity of the paratope arises from the hypervariable nature of the CDR loops, enabling an estimated 10^8 to 10^11 unique antibody specificities in the human repertoire through combinatorial V(D)J recombination and somatic hypermutation.^[9] While CDRs L1, L2, H1, and H2 often adopt a limited set of canonical conformations determined by loop length and key framework residues—identified via X-ray crystallography of immunoglobulin structures—CDR-H3 exhibits greater variability in length and shape, contributing significantly to paratope uniqueness.^[10] Nuclear magnetic resonance (NMR) spectroscopy has further revealed dynamic aspects of these conformations in solution, complementing crystallographic data.^[11] At the binding interface, typically 15-20 amino acid residues from the paratope contact 10-20 residues on the epitope, burying approximately 600-900 Å² of solvent-accessible surface area through non-covalent interactions such as hydrogen bonds, van der Waals forces, and electrostatic interactions.^[12] These contacts are concentrated in the CDRs, with CDR-H3 often playing a central role in defining specificity due to its structural prominence.^[13] The paratope exhibits conformational flexibility, particularly in the CDR loops, allowing adaptation to antigen binding via an induced fit mechanism where initial docking induces subtle rearrangements in loop positions to optimize complementarity and affinity.^[14] This flexibility is evident in structural comparisons of free and antigen-bound Fab fragments, where CDR-H3 loops can shift by several angstroms to accommodate diverse epitopes.^[15]

Function

Antigen Recognition

The specificity of the fragment antigen-binding (Fab) region arises from the precise shape and charge complementarity between its paratope—the antigen-binding surface formed by the complementarity-determining regions (CDRs)—and the epitope on the antigen. This non-covalent interaction ensures selective recognition of diverse antigens, including proteins, carbohydrates, and haptens, where epitopes can be linear (sequential amino acid residues) or conformational (discontinuous residues brought together by the antigen's three-dimensional structure).^[16]^[17] Affinity quantifies the strength of this Fab-antigen interaction and is measured by the equilibrium dissociation constant (K_d = k_off/k_on), which typically ranges from 10⁻¹² to 10⁻⁹ M for monoclonal Fabs, reflecting high binding stability post-affinity maturation. While full antibodies exhibit enhanced avidity through bivalent binding, the intrinsic monovalent affinity of a single Fab remains the primary determinant of its recognition capability.^[18]^[16] Binding kinetics govern the dynamic process of antigen recognition, with the association rate constant (k_on) typically on the order of 10⁵–10⁷ M⁻¹ s⁻¹, largely diffusion-limited, facilitating rapid initial encounter. The dissociation rate constant (k_off) then dictates the complex's longevity, with slower off-rates (around 10⁻³–10⁻⁵ s⁻¹) contributing to prolonged stability and effective antigen capture.^[16]^[19] Some Fabs display cross-reactivity or polyspecificity, binding multiple epitopes, which stems from germline-encoded features allowing broad initial recognition of diverse antigens. Somatic hypermutation subsequently refines this into higher specificity and affinity, reducing polyspecificity while preserving immune versatility.^[20]

Role in Immune Response

The fragment antigen-binding (Fab) region plays a pivotal role in initiating the humoral immune response by directly neutralizing pathogens. Through high-affinity binding to specific epitopes, the Fab sterically hinders pathogen attachment to host cells or blocks critical receptor interactions, thereby preventing infection. For instance, Fab-mediated neutralization inhibits viral entry into cells by occluding viral glycoproteins essential for fusion with host membranes.^[21]^[22] Beyond direct neutralization, the Fab facilitates downstream effector functions by tethering antigens to the antibody's Fc region. Antigen-bound Fabs target immune complexes for opsonization, enhancing phagocytosis by macrophages and neutrophils through Fc receptor recognition on these cells. Similarly, the exposed Fc domain promotes complement activation, leading to pathogen lysis via the classical pathway.^[23]^[24]^[25] In adaptive immunity, the Fab region of the membrane-bound B-cell receptor (BCR) is essential for antigen recognition and B-cell activation. Upon binding soluble or cell-surface antigens, the BCR-associated Fab triggers intracellular signaling cascades, including phosphorylation of ITAM motifs in the associated Igα/Igβ chains, which initiate B-cell proliferation, differentiation into plasma cells, and somatic hypermutation for affinity maturation.^[26]^[27]^[28]

Production

Enzymatic Methods

Enzymatic methods for producing fragment antigen-binding (Fab) regions involve proteolytic cleavage of intact antibodies, primarily immunoglobulin G (IgG), using specific enzymes to isolate the antigen-binding portions while separating them from the crystallizable fragment (Fc). These techniques were pioneered in the late 1950s and have evolved to include more precise bacterial enzymes. The foundational approach was described by Rodney R. Porter in 1959, who used crystalline papain to digest rabbit γ-globulin and antibodies, yielding fragments that retained antigen-binding activity. Papain, a cysteine protease derived from papaya latex, cleaves the IgG heavy chain above the hinge region's disulfide bonds, producing two monovalent Fab fragments (each approximately 50 kDa) and one Fc fragment (approximately 50 kDa). Optimal conditions for papain digestion include a pH of 6.5–7.5, a temperature of 37°C, and activation with reducing agents like 10–20 mM cysteine or β-mercaptoethanol to maintain the enzyme's catalytic cysteine residue in its reduced form.^[29] Digestion typically proceeds for 4–16 hours, with an enzyme-to-substrate ratio of 1:50 to 1:100 (w/w), ensuring high yields of functional, monovalent Fabs suitable for applications requiring reduced Fc-mediated effects.^[30] Pepsin digestion offers an alternative for generating bivalent fragments. Pepsin, an aspartic protease from porcine gastric mucosa, cleaves IgG below the hinge region's disulfide bonds, producing a single F(ab')₂ fragment (approximately 100 kDa) that retains bivalency due to the intact inter-Fab disulfide linkage, along with smaller Fc remnants that are often degraded further.^[31] This method is performed at a mildly acidic pH of 4.0–4.5 and 37°C, with digestion times of 8–18 hours and an enzyme-to-substrate ratio of 1:50 to 1:200 (w/w).^[32] To obtain monovalent Fab' fragments from F(ab')₂, mild reduction with agents like 2-mercaptoethylamine or dithiothreitol is applied, followed by alkylation to prevent re-formation of disulfides; this approach preserves some bivalency in intermediate steps for enhanced avidity in certain assays.^[5] More recently, the IgG-degrading enzyme of Streptococcus pyogenes (IdeS), a cysteine protease identified in the early 2000s, provides a highly specific alternative for Fab production. IdeS cleaves human IgG subclasses (1–4) at a single site in the lower hinge region, initially yielding an F(ab')₂-like fragment and an Fc/2 fragment; further incubation or secondary processing generates two Fab fragments and two Fc/2 pieces. This enzyme operates optimally at pH 6.0–7.0 and 37°C, with digestion completing in as little as 10–30 minutes at an enzyme-to-substrate ratio of 1:100 to 1:500 (w/w), offering faster and more uniform cleavage compared to papain, which can produce heterogeneous products due to non-specific activity. IdeS specificity minimizes over-digestion, making it advantageous for processing therapeutic IgGs across subclasses.^[33] Following enzymatic digestion, purification of Fab fragments typically involves affinity chromatography to separate them from Fc and undigested IgG. Protein A chromatography is commonly used, as it selectively binds the Fc fragment and intact IgG under neutral pH conditions, allowing Fabs to pass through in the flow-through or be eluted under low-pH conditions after Fc removal.^[34] Subsequent steps may include size-exclusion chromatography for polishing and removal of aggregates, ensuring high-purity Fabs (>95%) for downstream use.^[35]

Recombinant Techniques

Recombinant techniques for producing fragment antigen-binding (Fab) regions involve genetic engineering to express the variable heavy (VH) and variable light (VL) domains along with their constant regions (CH1 and CL) in host cells, enabling scalable and customizable production without relying on animal-derived antibodies. These methods typically use expression vectors that encode the Fab components, either as separate chains co-expressed or as linked constructs, to assemble functional heterodimers in vivo. This approach addresses the heterogeneity and low yields often seen in enzymatic digestion of polyclonal antibodies by allowing precise control over sequence design and post-translational modifications. Common expression systems include bacterial, yeast, and mammalian cells, each optimized for Fab folding and functionality. In Escherichia coli, periplasmic expression is favored due to the oxidizing environment that promotes proper disulfide bond formation in the Fab's VH-CH1 and VL-CL chains; vectors like pET-based plasmids are used to secrete the light chain and heavy chain fragment separately, achieving yields of 1-10 mg/L in shake flasks. Yeast systems, such as Pichia pastoris, leverage methanol-inducible promoters (e.g., AOX1) for high-density fermentation, producing glycosylated Fabs at 100-500 mg/L, though hyper-glycosylation can sometimes affect antigen binding. Mammalian cells, particularly Chinese hamster ovary (CHO) lines, provide the most native-like glycosylation and assembly, with stable transfection using glutamine synthetase selection yielding up to 1-5 g/L in bioreactors after process optimization. Single-chain variable fragment (scFv) variants serve as Fab precursors, where VH and VL are fused by a flexible linker such as (Gly4Ser)3 to create a single polypeptide, simplifying cloning into phagemid vectors for initial screening. While scFvs facilitate easier genetic manipulation and library construction, they can suffer from misfolding or reduced stability due to intramolecular interactions, prompting conversion to full Fabs by co-expression with constant domains or proteolytic processing for enhanced bivalency and half-life. This modular design allows rapid iteration in antibody engineering workflows. Compared to enzymatic methods, recombinant production offers scalability through bioreactor cultivation, customization via site-directed mutagenesis (e.g., CDR grafting for humanization to reduce immunogenicity), and ethical advantages by eliminating animal immunization. Optimized processes in CHO cells have demonstrated yields exceeding 5 g/L for humanized Fabs, supporting industrial-scale manufacturing for research and preclinical studies. Post-2020 advances have enhanced Fab production efficiency and diversity. Phage display libraries, expanded with synthetic VH/VL repertoires, enable affinity maturation of Fabs through iterative panning, achieving sub-nanomolar affinities for novel antigens as demonstrated in selections against SARS-CoV-2 spike proteins.^[36] Additionally, CRISPR-Cas9 editing of CHO cell lines has introduced targeted knock-ins for stable, high-fidelity Fab expression, facilitating the generation of bispecific Fabs by co-transfecting orthogonal light chains, with productivity increases of 2-3 fold over wild-type hosts.^[37] These innovations support faster development of multispecific therapeutics while maintaining structural integrity. In 2025, platforms for rapid antibody fragment production have enabled high-throughput generation of scFvs and Fabs in weeks using optimized expression systems.^[38]

Applications

Therapeutics

Fragment antigen-binding (Fab) regions have been engineered into therapeutic agents since the 1980s, offering targeted treatment for conditions ranging from toxin overdoses to chronic inflammatory diseases.^[39] One of the earliest approved Fab-based drugs is digoxin immune Fab (Digibind), introduced in the 1980s as an antidote for life-threatening digoxin toxicity in patients with heart conditions.^[40] This ovine-derived polyclonal Fab binds circulating digoxin, neutralizing its effects and facilitating renal excretion.^[41] Similarly, CroFab, approved by the FDA in 2000, consists of ovine Fab fragments specific to North American pit viper venoms, effectively neutralizing toxins to halt local tissue damage and systemic effects like coagulopathy.^[42] In ophthalmology, ranibizumab (Lucentis), a recombinant humanized monoclonal Fab approved in 2006, inhibits vascular endothelial growth factor (VEGF) to treat neovascular age-related macular degeneration through intravitreal injection, preserving vision by reducing retinal edema and angiogenesis.^[43] The therapeutic advantages of Fab fragments stem from their structural properties: lacking the Fc domain enables rapid renal clearance, minimizing prolonged systemic exposure and off-target effects.^[39] This also contributes to reduced immunogenicity compared to full antibodies, as the absence of Fc lowers the risk of anti-drug antibody formation and immune activation.^[44] Additionally, the smaller size (~50 kDa) enhances tissue penetration, allowing better access to targets in dense environments like tumors or inflamed joints.^[4] However, the short half-life (hours to days) poses a challenge for chronic indications, addressed in part by pegylation, as seen with certolizumab pegol (Cimzia), a PEGylated Fab' fragment targeting TNF-α. Approved for rheumatoid arthritis in 2009, it extends circulation time to weeks, improving efficacy in reducing joint inflammation and disease progression when combined with methotrexate.^[45] Emerging bispecific Fab formats expand therapeutic potential by enabling dual targeting, such as in cancer immunotherapy where one arm engages tumor antigens and the other recruits immune effectors.^[46] Dual-variable domain-immunoglobulin (DVD-Ig) constructs attach an additional variable domain to each Fab arm for bivalent bispecific binding without chain mispairing issues.^[47] CrossMab technology, introduced in 2011, facilitates correct heavy-light chain pairing in bispecific Fabs by swapping domains, supporting formats for simultaneous antigen blockade in oncology.^[48] In inflammatory diseases, ozoralizumab, a trivalent bispecific molecule incorporating a humanized anti-albumin Fab for half-life extension alongside anti-TNF nanobodies, has shown efficacy in rheumatoid arthritis patients with inadequate methotrexate response; approved in Japan in 2022, it remains in global clinical trials as of 2025, demonstrating sustained TNF neutralization with reduced dosing frequency.^[49]^[50] To overcome half-life limitations, advances include Fc-engineered Fab hybrids that fuse the Fab to modified Fc domains for neonatal Fc receptor binding, extending serum persistence while retaining monovalent targeting.^[39] These formats address gaps in autoimmune therapy, with ongoing developments in 2023-2025 focusing on engineered Fabs for conditions like rheumatoid arthritis, building on established approvals to enhance specificity and durability.^[39]

Diagnostics and Research

In vitro diagnostics frequently employ labeled Fab fragments for enhanced antigen detection in assays such as enzyme-linked immunosorbent assay (ELISA) and flow cytometry. In ELISA, primary antibody-Fab complexes allow for precise antigen quantification by reducing nonspecific binding and maintaining high affinity, with ratios as low as 1:1 preserving sensitivity comparable to traditional methods.^[51] In flow cytometry, Fab fragments facilitate live-cell labeling without requiring Fc blocking, as their lack of Fc regions minimizes interactions with Fc receptors on cells, thereby improving signal specificity for surface antigen analysis.^[52] The smaller size of Fabs (approximately 50 kDa) compared to full IgG molecules enhances tissue penetration and reduces background noise, leading to greater assay sensitivity in quantifying low-abundance antigens.^[53] Fab fragments have been pivotal in molecular imaging, particularly as radiolabeled agents for tumor visualization. In the 1990s, arcitumomab, a 99mTc-labeled anti-carcinoembryonic antigen (CEA) Fab' fragment, was developed for scintigraphic imaging of colorectal cancer metastases, offering rapid clearance and high tumor contrast due to its monovalent binding and reduced immunogenicity.^[54]^[55] More recently, as of 2025, positron emission tomography (PET) tracers incorporating 89Zr-labeled Fabs, such as [89Zr]Zr-Df-Fab-PAS200, have advanced oncology imaging by providing superior in vivo stability, high tumor-to-background ratios, and detailed pharmacokinetics in preclinical models of solid tumors.^[44] In structural biology research, Fab fragments serve as essential tools for protein crystallization and co-crystallization with antigens, stabilizing flexible regions and promoting lattice formation for X-ray diffraction studies. For instance, Fabs have enabled high-resolution structures of challenging proteins like parathyroid hormone-related protein by binding specific epitopes and facilitating crystal contacts.^[56] Additionally, nanobody-Fab fusions have revolutionized cryo-electron microscopy (cryo-EM) by acting as fiducials to enhance particle alignment and size for small proteins, allowing resolutions below 3 Å in membrane protein complexes.^[57]^[58] Recent advances in 2024-2025 have integrated recombinant Fabs into high-throughput screening platforms for proteomics, including multiplexed antibody arrays that enable simultaneous detection of hundreds of analytes with improved specificity over whole antibodies. These developments, such as phage display-derived Fab libraries screened via gel microdroplet fluorescence-activated cell sorting, accelerate the identification of novel binders for proteomic profiling and biomarker discovery.^[59]^[60]

References

[1]
The structure of a typical antibody molecule - Immunobiology - NCBI
These are termed the Fab fragments, for Fragment antigen binding. The Fab fragments correspond to the two identical arms of the antibody molecule, which contain ...3-3. The antibody molecule... · 3-4. The immunoglobulin...
[2]
Fragment Antigen-Binding - an overview | ScienceDirect Topics
Fab fragments are defined as the specific regions of antibodies that bind to target antigens, consisting of a light chain and a heavy chain, each containing ...
[3]
Separation and Isolation of Fractions of Rabbit Gamma-Globulin ...
Separation and Isolation of Fractions of Rabbit Gamma-Globulin containing the Antibody and Antigenic Combining Sites. R. R. PORTER. Nature volume 182, pages 670 ...Missing: Rodney | Show results with:Rodney
[4]
Fab Antibody: Definition, Structure, and Production | Sino Biological
The Fab (fragment antigen binding) fragment is the antibody binding region of an antibody. It contains one complete L chain and the V and CH1 portion of one H ...
[5]
Antibody Fragmentation | Thermo Fisher Scientific - US
Fab (50,000 daltons) is a monovalent fragment that is produced from IgG and IgM, consisting of the VH, CH1 and VL, CL regions, linked by an intramolecular ...<|control11|><|separator|>
[6]
Antibody Structure and Function: The Basis for Engineering ...
The intact antibody molecule shown in Figure 1 has three functional components, two Fragment antigen binding domains (Fabs) and the fragment crystallizable (Fc) ...
[7]
Research progress on unique paratope structure, antigen binding ...
Nov 21, 2022 · In conventional IgG antibodies, the forms of paratopes are usually a cavity, groove, or flat surface, with an epitope of 600-900 Å (the size ...
[8]
Antibody Structure | Microbiology Spectrum - ASM Journals
The Fab fragment recognizes antigen using some or all of its six complementarity-determining region (CDR) loops (three from each light and heavy chain), which ...<|control11|><|separator|>
[9]
Precise determination of the diversity of a combinatorial antibody ...
Antibody repertoire diversity, potentially as high as 1011 unique molecules in a single individual, confounds characterization by conventional sequence ...
[10]
Canonical structures for the hypervariable regions of immunoglobulins
Abstract. We have analysed the atomic structures of Fab and VL fragments of immunoglobulins to determine the relationship between their amino acid sequences and ...
[11]
Origins of specificity and affinity in antibody–protein interactions
Paratope hot spot residues are mostly buried in the antibody–antigen interaction interface (15). The predicted hot spot paratope residues (with PPI_CL ...
[12]
Structural analysis of B-cell epitopes in antibody:protein complexes
Jul 10, 2012 · The average epitope was found to be made up of ~15 residues with one linear stretch of 5 or more residues constituting more than half of the ...
[13]
Antibody-Antigen Binding Interface Analysis in the Big Data Era
Jul 13, 2022 · The structural analysis of the antigens in our database shows that on average the epitope contains 14.6 ± 4.9 residues, thus it is similar in ...
[14]
Do antibody CDR loops change conformation upon binding? - PMC
First, the 'lock-and-key' model states that there is little conformational change upon binding. Second, the 'induced-fit' model suggests that the bound ...
[15]
Flexibility and molecular recognition in the immune system - PNAS
The binding site flexibilities may result in varying mechanisms of antigen recognition including lock-and-key, induced-fit, and conformational selection.
[16]
The Structural Basis of Antibody-Antigen Recognition - Frontiers
Antibody epitopes (sometimes referred to as B-cell epitopes) are the molecular structures within an Ag that make specific contacts with the Ab paratope. B-cell ...
[17]
Understanding the complementarity and plasticity of antibody ... - NIH
Jun 29, 2023 · We have explored the structural landscapes of antibody–antigen interfaces to identify the structural determinants driving target recognition.
[18]
Measuring Affinity Constants of 1450 Monoclonal Antibodies to ... - NIH
We here report a microarray-based label-free assay platform for high-throughput measurements of monoclonal antibody affinity constants to antigens immobilized ...
[19]
Characterization of monoclonal antibody's binding kinetics using ...
The OIRD platform was used to determine Kon and Koff values of mAbs, and to measure avidity values of mAbs in a high-throughput and cost-effective way.
[20]
Human Germline Antibody Gene Segments Encode Polyspecific ...
Apr 25, 2013 · We investigated whether germline gene-encoded antibodies are optimal for polyspecificity by determining the basis for recognition of diverse antigens.
[21]
Neutralizing Antibodies: Role in Immune Response and Viral Vector ...
May 29, 2025 · Two antigen-binding fragments, known as Fab, are responsible for pathogen binding and neutralization [12]. These fragments are linked to the ...
[22]
Different mechanisms of antibody-mediated neutralization of ... - NIH
Both neutralizing and non-neutralizing Fabs bound to the B site of the capsids, showing that neutralization depends on specific interactions of the Fabs with ...
[23]
Beyond neutralization: Fc-dependent antibody effector functions in ...
Dec 19, 2022 · Whereas the antigen-binding fragment (Fab) region of antibodies directly binds to antigen, the Fc region determines the antibody isotype and ...
[24]
Beyond binding: antibody effector functions in infectious diseases
Fab domains are essential to the adaptive nature of the humoral response and evolve during an immune response to improve affinity to a foreign antigen. The Fc ...
[25]
The role of Fc–FcγR interactions in IgG-mediated microbial ... - NIH
In the context of infectious diseases, Fc–FcγR interactions readily amplify the in vivo protective activity of neutralizing antibodies through opsonization and ...
[26]
Antigen footprint governs activation of the B cell receptor - Nature
Feb 22, 2023 · Antigen binding by B cell receptors (BCR) on cognate B cells elicits a response that eventually leads to production of antibodies.
[27]
A structural platform for B cell receptor signaling - PubMed Central
Sep 15, 2022 · B cell activation is triggered by antigen recognition by the B cell receptor (BCR), resulting in B cell proliferation and affinity maturation ...
[28]
It's All About Change: The Antigen-driven Initiation of B-Cell ...
B-cell responses are initiated by the binding of foreign antigens to the clonally distributed B-cell receptors (BCRs) resulting in the triggering of signaling ...
[29]
Cytokine Activation by Antibody Fragments Targeted to ... - NIH
Antibody fragments have been designed that recognize cytokine-receptor complexes and change cytokine biological activity profiles.
[30]
Targeted modulation of immune cells and tissues using engineered ...
Sep 28, 2023 · Targeting of immune cells can be achieved using traditional protein engineering strategies, employing monoclonal antibodies, engineered binding ...
[31]
https://www.promegaconnections.com/using-pepsin-to-prepare-fab2-fragments-and-determine-deuterium-exchange/
[32]
Soluble Papain to Digest Monoclonal Antibodies; Time and Cost ...
May 12, 2022 · Here we report a time and cost-effective method to produce pure, active and stable Fab using soluble papain. Large laboratory scale digestion ...
[33]
Using Pepsin to Prepare F(ab')2 Fragments - Promega Connections
Apr 27, 2012 · To produce an F(ab')2 fragment, IgG is digested with pepsin, which cleaves the heavy chains near the hinge region. One or more of the disulfide ...
[34]
Optimization of Enzymatic Antibody Fragmentation for Yield ... - NIH
A systematic approach optimizes antibody fragmentation by testing pH, enzyme concentration, and reaction time, with pH having the greatest impact. This avoids ...Missing: activation | Show results with:activation
[35]
A new tool for monoclonal antibody analysis: Application of IdeS ...
Apr 7, 2014 · IdeS proteolysis uses the enzyme IdeS to cleave IgG heavy chains, releasing domains for characterization of domain-specific modifications.
[36]
Papain digestion of mAb and transient expression in mammalian cells
After digestion, separation of the Fab fragment from the Fc (fragment that crystallizes) and residual intact antibody was achieved using protein A affinity ...
[37]
Two routes for production and purification of Fab fragments in ...
One route utilizes papain digestion of an intact monoclonal antibody for Fab fragment production. After digestion, separation of the Fab fragment from the Fc ...
[38]
David vs. Goliath: The Structure, Function, and Clinical Prospects of ...
Fab fragments are composed of an antibody light chain (VL + CL domains) linked by a disulphide bond to the antibody heavy chain VH and CH1 domains; the ...
[39]
Digoxin Immune Fab - StatPearls - NCBI Bookshelf
Jun 22, 2024 · Digoxin immune Fab is an antidote for digoxin toxicity, a condition typically observed in patients with atrial fibrillation and underlying heart failure.
[40]
[PDF] Package Insert - DigiFab - FDA
Prior treatment with digoxin-specific ovine immune Fab carries a theoretical risk of sensitization to ovine serum protein and possible diminution of the ...
[41]
[PDF] Package Insert - CROFAB - FDA
CROFAB is a venom-specific Fab fragment of immunoglobulin G (IgG) that works by binding and neutralizing venom toxins, facilitating their redistribution ...
[42]
[PDF] Clinical Pharmacology Biopharmaceutics Review(s)
Fab as a therapeutic agent to treat patients with age-related macular degeneration (AMD). The observed ranibizumab serum concentrations following ...
[43]
Advances in immunoPET/SPECT imaging: The role of Fab and F(ab′)
These fragments, devoid of the immunoglobulin Fc region, are cleared more rapidly from the blood, exhibit lower immunogenicity, and have a shortened half-life, ...
[44]
Certolizumab pegol: in rheumatoid arthritis - PubMed
Certolizumab pegol is a PEGylated humanized Fab' monoclonal antibody that targets and neutralizes both membrane-bound and soluble tumor necrosis factor ...
[45]
Bispecific antibodies in cancer immunotherapy - PMC - NIH
The anti-EpCAM Fab fragment of catumaxomab can bind to tumor cells that express EpCAM, and anti-CD3 Fab of catumaxomab can recruit T lymphocytes to tumor cells.
[46]
Bispecific Antibody Formats - #site_title - evitria
Jul 5, 2024 · The Fab arms of a DVD-Ig are symmetrical and can each bind to two different targets, avoiding issues with heavy and light chain mispairing.
[47]
Ten years in the making: application of CrossMab technology for the ...
CrossMab technology was described in 2011 as novel approach enabling correct antibody light-chain association with their respective heavy chain in bispecific ...
[48]
Ozoralizumab: First Approval - Semantic Scholar
In September 2022, ozoralizumab was approved in Japan for the treatment of RA that is inadequately managed by current available treatments.
[49]
https://www.semanticscholar.org/paper/Ozoralizumab%253A-First-Approval-Keam/9ef2c22e8cb71739895f75a4c76426a14002310c
[50]
Myasthenia gravis in 2025: five new things and four hopes for the ...
Feb 22, 2025 · Our 'five new things' include thymectomy, new immunotherapies, recent guidelines, progress in biomarkers, and the concept of MG 'age' and 'stage'.
[51]
Primary antibody-Fab Fragment Complexes - PubMed
Using complexes containing Fab fragments that recognize both the Fc and F(ab')2 regions of IgG, we show that this approach prevents nonspecific labeling of ...
[52]
https://www.cellsignal.com/learn-and-support/technical-support/fc-blocking-fab-antibody-fragments-live-cell-flow-cytometry/000002032
[53]
Unlocking the Power of Immunoglobulin F(ab) and F(ab')2 Fragments
Both F(ab) and F(ab')2 fragments consist of one or two Fab regions, respectively, which retain the antigen-binding specificity of the full-length antibody.
[54]
99mTc-Arcitumomab - Molecular Imaging and Contrast Agent ... - NCBI
Dec 11, 2005 · 99m Tc-IMMU-4 is not indicated for the differential diagnosis of suspected colorectal carcinoma or as a screening tool for colorectal cancer.
[55]
Tc-99m-Arcitumomab (CEA-Scan) - AuntMinnie
Apr 2, 2002 · Arcitumomab (CEA-Scan) is a murine monoclonal Fab' fragment, generated from IMMU-4 directed against the CEA surface antigen found on colorectal carcinomas.
[56]
Antibody fragments as tools in crystallography - PMC - NIH
More recently, a Fab fragment has been used to aid the crystallization of parathyroid hormone-related protein (PTHrP), with diffraction to 2 Å resolution ...
[57]
Development of a universal nanobody-binding Fab module for ... - NIH
We developed a synthetic Fab (NabFab) that rigidly binds the conserved scaffold of nanobodies, providing a universally applicable fiducial for cryo-EM studies.
[58]
Cryo-EM structure determination of small proteins by nanobody ...
We describe a general method that allows structure determination of small proteins by single-particle cryo-electron microscopy (cryo-EM).
[59]
High-throughput strategies for monoclonal antibody screening
May 8, 2025 · This review explores recent advancements in high-throughput development of antibody, highlighting their potential advantages over traditional methods and their ...
[60]
Going native: Direct high throughput screening of secreted full ...
Gel microdroplet – fluorescence activated cell sorting (GMD-FACS) is an innovative high throughput screening platform for recombinant protein libraries, and we ...<|separator|>