Originally conceptualized in the 1970s, monoclonal antibodies have evolved from a pioneering laboratory breakthrough into a widely used and essential technology with significant clinical applications, including the treatment of cancer, autoimmune disorders, and infectious diseases.

Traditionally, antibodies were developed through immunization of a host animal to generate an immune response, followed by harvesting and purifying of antibodies present in the blood. This approach produces a polyclonal mixture of antibodies. In contrast, the development of monoclonal antibodies focuses on producing a single antibody that is highly specific to a single epitope.

These antibodies can be developed using a range of techniques, but commonly through phage display, B cell technologies or cell fusion-based hybridoma approaches. In the hybridoma process, the most established method, B cells from immunized animals are fused with myeloma cells to form hybridoma cells. These hybridomas generate large quantities of identical monoclonal antibodies, each specifically targeting the desired epitope.

Applications of monoclonal antibodies in laboratory techniques

Monoclonal antibodies can be used in a wide range of applications across both native and denatured epitope detection. Common research applications for monoclonal antibodies include western blotting, immunohistochemistry, immunocytochemistry, flow cytometry and immunoprecipitation. Monoclonal antibodies, when well characterized to confirm intended binding to the target, provide highly specific and reproducible results, making them ideal for detecting target proteins with precision.

While monoclonal antibodies offer high specificity by targeting a single epitope, they lack the multi-epitope recognition characteristic of traditional polyclonal antibodies. This multi-epitope binding can be advantageous in applications such as detecting low-abundance targets or performing immunoprecipitation. However, the precise single-epitope recognition and batch-to-batch consistency of monoclonal antibodies provide more reproducible research results. To combine these benefits, many reagent companies now offer polyclonal mixtures of recombinant monoclonal antibodies, effectively merging the advantages of both polyclonals and monoclonals.

Monoclonal antibody development steps

Several crucial processes, ranging from antigen design and immunization to antibody isolation and screening, are involved in the creation of monoclonal antibodies. Careful planning and execution of each stage is necessary to guarantee that the final antibodies have the appropriate functionality, sensitivity and specificity for their intended use.

Antigen selection and preparation

Antigens for antibody discovery can be purchased from commercial suppliers or designed and synthesized. Antigen quality is essential for successful monoclonal antibody production, as it directly influences the specificity and effectiveness of the immune response. Highly purified antigens are crucial, as even minor impurities can lead to non-specific antibody production.

Before immunization, antigens must be carefully prepared, free from endotoxins, extreme pH levels, and other buffer components that could harm animal welfare and impact the immune response. Using an appropriate diluent is key to ensuring antigen stability as well as safety and effectiveness.

Immunization process

In in vivo mAb development, immunization introduces an antigen into a host animal to stimulate an immune response. Pre-immunization screening helps confirm that the animal lacks pre-existing antibodies against the target antigen, enabling precise immune monitoring in response to the new antigen. Typically, adjuvants are used to enhance the immune response and the production and proliferation of B cells secreting antibodies specific to the antigen.

After a series of immunizations, blood samples are taken to evaluate the antibody response. Once a strong response is confirmed, researchers harvest the animal's immune tissue (commonly the spleen) to isolate splenocytes, from which the right antigen-secreting cells (ASCs) can be identified to produce the antibody. There are two main methodologies for antibody generation from B cells - hybridoma techniques and B cell sorting techniques.

Identifying and isolating antibody-secreting cells

After immunization, antibody-secreting cells, primarily B cells, are isolated from the spleen or lymph nodes of the immunized animal. Next, cells producing antibodies and exhibiting high affinity and specificity for the target antigen are screened. Techniques including ELISA, flow cytometry, or limiting dilution assays are used to examine antibody secretion and binding characteristics. These identified B cells serve as the basis for hybridoma generation or other monoclonal antibody production methods.

Hybridoma technology

Hybridoma technology has transformed biomedical research and clinical medicine by providing a reliable, scalable way to produce antibodies that can precisely target molecules, cells, or pathogens. Hybridoma technology involves fusing antibody-secreting B cells with myeloma cells, creating hybridoma cells that secrete the antibody and can proliferate indefinitely in culture.

The hybridoma technique, invented by Georges Kohler and César Milstein in 1975, has evolved significantly, becoming a cornerstone for monoclonal antibody production. The key aspects of its evolution include:

• Improved fusion methods to optimize fusion efficiency and reduce cell damage.
• Selection of myeloma cell lines engineered to not produce their own antibodies, ensuring hybridomas produce only the desired monoclonal antibodies.
• Direct isolation and fusion of single B cells, potentially increasing antibody diversity.
• Application of robotic systems and automated cell sorting to rapidly screen large hybridoma libraries for the most specific and potent antibodies.
• Utilization of recombinant DNA techniques, such as chimerization and humanization, to modify antibodies from typical host species like mice or rabbits, making them more human-like and reducing immunogenicity for clinical use.

B cell isolation and fusion

B cell isolation is a critical step in producing monoclonal antibodies, which can start from spleen cells, peripheral blood mononuclear cells (PBMCs) or lymphoid tissues. There are 4 main types of B cells, and the B cell subtype used for isolation depends on the type of method and technology used. Typically, memory B cells are the most common subset accessed.
Antigen-specific B cells can be isolated using techniques like fluorescence-activated cell sorting (FACS) or magnetic bead separation. Purified B cells (or crude splenocyte mixtures) are fused with myeloma cells using chemical agents like polyethylene glycol (PEG) or electric pulses (electrofusion) to create hybridomas capable of producing monoclonal antibodies.

Cloning and expansion of hybridomas

After fusion, hybridoma cells are cloned to ensure that each colony originates from a single cell, ensuring monoclonality (a single species of antibody is produced). This is commonly done using limiting dilution, cloning in a semi-solid medium or automated methods like flow cytometric single-cell sorting. Once clonal, the hybridomas are expanded in culture to produce sufficient quantities of the desired monoclonal antibodies, which are then screened for antigen specificity and yield.

B cell sorting

B cell sorting is the process of isolating and categorizing B cells based on specified criteria, frequently performed by flow cytometry or magnetic beads. Effective sorting of individual B cells in a single-cell manner enables sequencing of the immunoglobulin genes and preservation of the natural pairing of the heavy and light chains. Native pairing can result in an antibody that has a higher chance of being specific and functional, as it is exactly the same antibody that was created during affinity maturation to the target antigen within the host.

Screening and selection of antibodies

During the development of monoclonal antibodies, effective screening is essential to identify candidates with the desired specificity and highest potential for therapeutic, diagnostic or research use. The process of antibody selection is critical in narrowing down a large pool of candidates to those with the most desirable characteristics.

Screening methods

Screening for effective monoclonal antibodies uses several high-throughput techniques to evaluate binding specificity, application performance (eg, western blotting, immunohistochemistry) and functional activity. Researchers commonly use enzyme-linked immunosorbent assay (ELISA) for preliminary screening to detect antibodies that bind to a specific antigen, but there are other types of screening that may be applicable, such as soluble assays (including homogenous time-resolved fluorescence (HTRF)), Octet (biolayer interferometry-BLI), or flow cytometry. In some cases, a combination of assays may be used.
The type of screening is dependent on the final use/application of the antibodies.

Antibody selection

Antibody selection focuses on identifying antibody clones that demonstrate the final desired characteristics/attributes that are required of the antibody. This may be high binding affinity, performance in specific proteomic applications like ChIP-sequencing or western blotting, or functional properties, such as neutralization or inhibition of receptor binding and pathway activation. After identifying potential candidates through screening assays, antibodies can be tested in a range of applications, including functional or cell-based assays, to confirm biological activity.

Selected antibodies must meet criteria for high specificity, good stability, and high-level production yields before advancing to the next stages of development. These rigorous selection steps ensure that only the most potent and suitable antibodies proceed to later stages of development.

Antibody characterization

Researchers typically determine the structural, physiochemical, and functional properties of antibodies during characterization to ensure the development of a stable antibody product. Common analytical techniques such as HP-LC, SDS-PAGE, and mass spectroscopy are used to assess the size, identity, aggregation, charge, glycosylation patterns, and post-translational modifications.

Researchers also detect impurities and assess antibody stability to ensure advancement in clinical or commercial applications.

Antibody expression, purification, and storage

One significant benefit of monoclonal antibody development is the ability to produce consistent amounts of antibody as needed, and in large amounts, without relying on immunization of a host animal (and the variance in immune response that may result). Culturing hybridoma cells in optimal conditions can give high yields of the antibody that can be produced as needed. Where antibodies are sequence-defined and converted into recombinant format, transient or stable transfection of the antibody-producing genes into common cell lines like HEK or Chinese hamster ovary (CHO) enables the production of the antibody as required.

Chromatography techniques play an essential role in the biopharmaceutical industry for separating and purifying molecules like monoclonal antibodies. Protein A or G chromatography provides high-purity antibody purification, while hydrophobic interaction, hydroxyapatite, and ion exchange chromatography can remove contaminants and aggregates during the polishing process. For the production of therapeutic or large-scale batches, integrating these methods into a continuous flow-through system enhances efficiency by eliminating intermediate steps and making bioprocessing more commercially viable.

Storing monoclonal antibodies maintains their stability, potency, and efficacy for various applications in research and clinical settings. Researchers often store un-modified antibodies at subzero temperatures (such as -80°C) for long-term preservation, using cryoprotectants like glycerol to prevent freeze-thaw damage. Short-term storage is typically at 4°C for immediate use. Employing proper storage methods and minimizing freeze-thaw cycles preserves the integrity and effectiveness of monoclonal antibodies over time.

Key technologies in monoclonal antibody discovery

Advances in monoclonal antibody discovery have resulted in a variety of available technologies, each offering different benefits and challenges. Ranging from traditional hybridoma techniques and B cell sorting to more advanced methods like phage display and recombinant DNA technology, these approaches have revolutionized the field of antibody development.

Hybridoma technology

Generating monoclonal antibodies through hybridoma technology offers key advantages:

• The pairing of constant and variable region gene combinations is preserved in the native form.
• As hybridoma technology entails immunizing an animal, the natural affinity maturation process of the immune system is advantageous to the resultant antibodies. High-affinity antibodies are produced as a result, compared to techniques like phage display.
• However, technology also presents challenges:
  Production is often lengthy and more expensive than polyclonal development.
• The process is vulnerable to contamination, and maintaining cell viability can be challenging. Avoiding contamination through aseptic techniques and appropriate laboratory practices, as well as generating and maintaining a cell bank of well-characterized clones, can help to protect specific antibody-producing lines from loss.
• Stable myeloma cell lines for human antibody production are lacking.
• The method requires known and available antigen targets.
• Due to the low fusion success rate, hybridoma cell fusion and isolation remain inefficient. The technique accesses only a small proportion of antibody-secreting cells from the host animal (<1%), which can make finding rare antibodies challenging.
• Competition among hybridomas in the same culture after PEG fusion, especially in early protocol steps, poses a challenge.
• Careful selection of antigen is important to retain its native conformation upon immunization, posing a bottleneck, as many antigens (eg, ion channels, GPCRs) are unavailable in solution or may not elicit the desired humoral response.
  The gradual accumulation of genetic changes in the hybridoma cells over time leads to genetic drift, which can lead to slight variations in the antibodies they produce compared to the original version. Slight alterations in the antibody's paratope, or binding site, can lead to changes in binding affinity or cross-reactivity with unintended targets. This issue is distinct from the batch-to-batch variability observed in polyclonal antibodies, which arises from using different animals or production cycles. Some hybridoma-derived cell lines may start to produce lower antibody yields or decline over passages, affecting both the quality of the antibody and its binding, as well as the effectiveness of large-scale production. This is particularly difficult for long-term GMP-grade bioreactor use as the consistency and quality of the final product may decline, necessitating continuous monitoring, re-cloning, and optimization of cell lines to ensure stable and reliable antibody production.
• Sequencing the antibody genes of hybridoma clones, and cloning these genes into a recombinant expression vector, is a technique used commonly to protect important monoclonal antibodies and ensure continued expression and use. The great advantage of recombinant antibodies is that they are not impacted by genetic drift, as they are produced using a stable, defined genetic sequence, ensuring consistent antibody structure and function across batches. This stability in recombinant antibodies eliminates the variability seen in hybridoma-derived antibodies, offering greater reliability in research applications.

In vitro display technologies

In vitro display technologies, such as yeast display and phage display, are used to screen for antibodies with high antigen affinity after creating a collection of highly diverse antibody DNA sequences, or an antibody library.

Phage display is a relatively well known used to study protein interactions and discover new monoclonal antibodies. This method involves displaying antibody fragments on the surface of bacteriophages, which are viruses that infect bacteria. By creating large combinatorial libraries of antibody fragments, researchers can screen for those that bind to specific antigens, enabling the discovery of highly targeted antibodies.

Following identification of the sequence of interest, the antibody genes are cloned into an expression vector and the protein is expressed in a host (bacteria, yeast, insect, or mammalian cell lines). Full-length antibodies typically need mammalian expression systems due to the presence of functionally and structurally significant glycosylation, whereas antibody fragments and antibody-like molecules are not glycosylated and can be generated more easily in E. coli-based production platforms.

• These synthetic in vitro technologies offer several advantages over in vivo discovery
• It allows for the rapid generation of antibodies with high specificity against antigens that are toxic or non-immunogenic.
• The in vitro nature of the method eliminates the need for animal models, making the process more ethical and less dependent on animals.
• Phage display can generate fully human antibodies, reducing the risk of adverse immune responses in therapeutic applications.
• Its flexibility allows for the discovery of various antibody formats, including single-chain variable fragments (scFvs) and full-length antibodies, enhancing their utility in both research and biopharmaceutical industries.
• Resulting antibodies identified from rounds panning and binding during the phage process can be affinity matured in vitro and the sequence modified to get the desired antibody binding profile and performance. This technique allows for protein engineering and the production of antibody forms such as bispecifics, multispecifics, and antibody fragments (eg, Fab, VHH, and scFv). This antibody engineering approach can also be applied to antibodies discovered in vivo which are sequenced.

Production of antibody chimeras

Monoclonal antibodies with modified constant regions or isotypes are commonly known as chimeras or ‘chimeric antibodies.’ This method involves cloning the variable region genes from a hybridoma and combining them with different constant region genes to switch antibody classes or species. For example, a rabbit IgG antibody (rabbits have only one IgG subtype) can have the Fc region switched to a mouse IgG1 backbone. This retains antigen specificity while giving more options for researchers to use the antibody in their application – eg, for multiplex imaging using a range of different conjugated secondary antibodies for detection.

Single B cell antibody technology

Single B cell antibody technology generates monoclonal antibodies by isolating and cloning immunoglobulin genes from individual B cells. This approach preserves the natural pairing of heavy and light chains, enabling the discovery of highly specific and functional antibodies.

Recombinant antibodies

Following in vivo antibody discovery via hybridoma or B cell isolation methods, or antibody discovery via synthetic libraries such as phage display, antibody genes are sequenced, cloned, and expressed in a host cell, resulting in recombinant antibody production. This method is more dependable and can be faster than traditional expression methods.

However, the most important advantage of recombinant antibodies is the consistency of results and batch-to-batch repeatability. Unlike polyclonals, where host response and purification cannot guarantee the same antibody mixture is produced during each round of manufacture, recombinant antibodies remain consistent time after time. This is critical to give the same assay results across samples, help researchers avoid repeating experiments, and give robust research outcomes that support reproducibility and accelerate research progress.
Standardization, through the use of recombinant monoclonal antibodies, eliminates batch-to-batch variability and ensures that the antibodies used are specific to their intended targets, reducing the chances of non-reproducible results.

Emerging technology - Cell-free protein synthesis

Cell-free protein synthesis is an innovative approach for producing monoclonal antibodies without the need for live cells, streamlining antibody development. Recently, cell-free systems based on Bacillus subtilis, Pseudomonas, and Vibrio have been optimized in the laboratory. There are detailed techniques for E. coli-based lysates. In eukaryotic CF systems, extracts from rabbit reticulocyte lysate, wheat germ, Spodoptera frugiperda 21, CHO, and human cells are commonly utilized. This method facilitates rapid and scalable synthesis of antibodies with functional assembly, including complex formats like IgG.

It offers advantages like flexible production scales, rapid and on-demand synthesis, minimal downstream processing, rapid optimization and screening, and allows the production of complex antibodies, making it valuable for accelerating early-stage antibody development and optimization. Furthermore, this system has the potential for site-specific modifications, such as the addition of non-canonical amino acids for the creation of antibody-drug conjugates, providing openness and configurational flexibility even for the synthesis of proteins that are challenging to express by avoiding the limitations of the cell membrane.

This is an exciting area of advancement, however not advanced enough at this time for robust widespread use at scale.

Quality control and research reproducibility

Quality control (QC) and reproducibility are important for consistent product quality and reliable research outcomes. QC ensures that monoclonal antibodies are free from contaminants and maintain batch-to-batch consistency, which is critical for consistent results and performance.

QC also addresses issues of antibody fragmentation and aggregation, which can reduce antibody performance. Abcam uses recombinant technology for all new products through application testing, and knockout and knock-down validation. For particular antibody targets, we also include enhanced validation procedures that address a variety of research needs, ranging from extensive immunohistochemistry data packs to routine testing in three species (human, mouse and rat), to characterization in up to 10 applications, ensuring researchers have access to the highest quality and most reliable antibodies available.

Our biophysical quality control (BPQC) technology generates a distinct molecular level "fingerprint" for every antibody product. We use advanced procedures such as liquid chromatography-mass spectrometry, dynamic light scattering, and high-performance liquid chromatography to ensure robust, reproducible results with excellent lot-to-lot consistency and specificity, with 75% of our recombinant antibodies having undergone BPQC.

As the majority of our antibodies are recombinant monoclonals we are able to apply these analytical techniques to confirm we are making exactly the same protein in each antibody batch.

This QC approach minimizes lot-to-lot variability, ensuring assay results are consistent and repeatable, and allowing researchers to combine batches from multiple production runs. This saves time, reduces assay re-optimization, and maintains consistency over long-term, complex experimental projects. Abcam's solution, which has received numerous international accolades (such as the CiteAb award in 2020 and 2022 and the digital science tool of the year award in 2024), strategically addresses the reproducibility challenge. By delivering antibodies with excellent specificity, sensitivity, and consistency, we enable researchers to progress their proteomic research with confidence, reduce manuscript corrections and retractions, and accelerate time to results.

FAQs

What are the key steps in the development of monoclonal antibodies?

The development of monoclonal antibodies involves several key steps, beginning with immunogen design, which involves identifying target antigens and immunogenic areas using computational techniques and structural analysis. This ensures that epitopes generate a significant immune response, which improves specificity and functionality. If using in vitro techniques, the same principle applies as the antigen is used to ‘pan’ or identify antibody binders from many candidates present in the antibody libraries being screened.

Following immunogen design, host animals are immunized and responses to the immunization are assessed through titer screening. Tissues are then harvested to isolate B cells and enable the identification of antibody-secreting cells that have responded to the immunization in the desired way and are secreting specific binders.

B cells are screened to assess whether they are binding the antigen, then fused with myeloma cells to generate hybridomas that proliferate and secrete antibodies in culture indefinitely (or sequenced and cloned into vectors that enable transient or stable transfection and subsequent expression of antibody). Following screening and isolation antibody, candidates are characterized in various assays that relate to the intended end-use (eg, immunohistochemistry, flow cytometry). Once antibodies are identified with desired characteristics they can be produced and purified at a larger scale.

How do genetic sequencing advancements impact monoclonal antibody development?

Advancements in recombinant DNA technology and genetic sequencing have significantly impacted monoclonal antibody development by enabling precise identification of the genetic makeup of target antigens and immune responses.

For instance, techniques like phage display and gene editing enable rapid screening and modification of antibody-expressing genes, making possible the development of humanized and fully human antibodies by optimizing antibody gene sequences for improved binding affinity and reduced immunogenicity.
Furthermore, sequencing methods enable the identification and isolation of specific genetic sequences that code for desired antibody characteristics and support a more optimized design of targeted and effective monoclonal antibodies. Thus, recombinant DNA technology and genetic sequencing accelerate the creation of highly specific and efficient monoclonal antibodies from diverse libraries, improving efficiency in research and clinical applications.