What Is Hybridoma Technology and How Is It Used?

Hybridoma technology is a laboratory method for producing large, consistent quantities of a single type of antibody by fusing an antibody-producing immune cell with an immortal cancer cell. The resulting hybrid cell, called a hybridoma, inherits the immune cell’s ability to make a specific antibody and the cancer cell’s ability to divide indefinitely. Developed by Georges Köhler and César Milstein in 1975, it earned them a Nobel Prize and remains one of the foundational techniques behind modern diagnostic tests and antibody-based therapies.

How a Hybridoma Is Made

The process starts with an animal, usually a mouse, that has been immunized with a target substance. Once the mouse mounts an immune response, its spleen is harvested. The spleen is rich in B cells, the white blood cells responsible for producing antibodies. These B cells are then mixed with myeloma cells, a type of bone marrow cancer cell that grows endlessly in culture but does not produce useful antibodies on its own. The two cell types are coaxed into merging, and the fused product is a hybridoma: a cell that secretes one defined antibody and can keep dividing in the lab indefinitely.¹

The trick is getting two very different cells to merge their membranes and combine into one. The classic method uses polyethylene glycol (PEG), a chemical that essentially pushes cell membranes together until they fuse. PEG is cheap, widely available, and does not require specialized equipment, which is why it has remained standard in most labs for decades. An alternative is electrofusion, where brief electric pulses open tiny pores in the cell membranes, allowing neighboring cells to merge. Direct comparisons have shown that electrofusion can yield roughly 4 to 33 times more hybridomas per batch of spleen cells, and the resulting cells tend to grow faster.² Despite those advantages, electrofusion has not replaced PEG in everyday practice. The instruments are expensive, the technique demands more operator expertise, and there is less published reference work for labs to draw on.³

Sorting Out the Winners

After fusion, the culture dish contains a messy mixture: unfused B cells, unfused myeloma cells, and the hybridomas you actually want. Only the hybridomas are useful, so the others need to be eliminated. This is done with a selective growth medium called HAT, which contains hypoxanthine, aminopterin, and thymidine. Aminopterin blocks a key pathway that cells normally use to build DNA. Unfused myeloma cells cannot survive because they lack an enzyme (HPRT) that would let them use the backup pathway supplied by hypoxanthine.⁴ Unfused B cells die naturally after a few days because they are not immortal. Only the hybridomas, which inherited HPRT from the B cell and immortality from the myeloma cell, survive and multiply.

Surviving in HAT medium does not guarantee that a hybridoma is making a useful antibody. Many fused cells secrete antibodies that bind the wrong target, bind weakly, or do nothing interesting at all. So the next step is screening: testing each hybridoma’s supernatant against the target antigen to identify the rare clones that produce antibodies worth keeping.

Screening for the Right Antibody

Traditional screening relies on enzyme-linked immunosorbent assays (ELISAs), where the target antigen is coated onto a plate and the hybridoma supernatant is added to see if anything sticks. ELISA works well for many applications, but it can miss antibodies that only recognize a protein in its natural three-dimensional shape on a living cell surface, and it can flag false positives when proteins stick nonspecifically to the plate.

Newer approaches use living cells as the screening platform. One method employs image cytometry, where hybridoma supernatants are tested directly against cells engineered to express the target antigen on their surface. This approach can detect positive antibodies at concentrations as low as about 5 nanograms per milliliter in the supernatant, and the entire screening procedure can be completed within a single day. Because the antibody is binding to a living cell, both false positives and false negatives drop compared to plate-based methods.⁵

Flow cytometry takes a similar cell-based logic and adds the ability to sort individual cells at high speed. One strategy labels the antigen with a fluorescent tag and lets it bind to the membrane-bound antibody on the hybridoma’s own surface; cells that light up are sorted one per well into a 96-well plate, skipping much of the tedious repeated screening and subcloning that older workflows require.⁶ For targets where you need an antibody that actually blocks a biological interaction rather than just binding, duplex flow cytometry assays can distinguish neutralizing from non-neutralizing antibodies in one shot, as demonstrated in a screening campaign for anti-PD-1 antibodies.⁷

Getting to a True Monoclonal Cell Line

Even after a promising hybridoma is identified, the well it came from usually contains more than one clone. Hybrid cells also tend to have unstable chromosome arrangements, which means a cell producing your desired antibody can be outgrown by neighboring cells that produce something else or nothing at all.⁸ To lock in stable antibody production, the cells must be subcloned down to a single cell.

The oldest and most common method is limiting dilution: cells are diluted into plates at a concentration low enough that most wells receive zero or one cell. The wells that grow are tested again for antibody secretion. Modified versions of this protocol use real-time fluorescence imaging to confirm that a colony genuinely arose from a single cell, rescuing interesting clones that might otherwise be lost in the traditional approach.⁹ Once a stable monoclonal line is established, it can be frozen, banked, thawed years later, and expected to produce the same antibody it always did.

Scaling Up Production

A monoclonal hybridoma line in a flask can produce milligrams of antibody, but many applications need more. Historically, the simplest way to scale up was to inject hybridoma cells into the abdominal cavity of a mouse, where they would form a tumor and secrete antibody into the fluid that accumulated (called ascites). This method yields concentrated antibody but causes animal suffering and produces a fluid contaminated with mouse proteins.

Bioreactor systems offer an in vitro alternative. Hollow-fiber bioreactors, for example, grow hybridoma cells at high density behind a semi-permeable membrane, allowing nutrients in and antibody-rich fluid out. Comparative studies have found that bioreactor output can match or approach that of mouse ascites. In one head-to-head test, 20 mice yielded between about 450 and 1,000 milligrams of antibody depending on the cell line, while bioreactors running for 65 days produced between roughly 170 and 1,020 milligrams.¹⁰ Dialysis-based bioreactors perform similarly and have the added benefit of producing antibody that is relatively free of contaminating protein, a persistent problem with ascites-derived material.¹¹ Today, regulatory agencies and institutional ethics boards strongly encourage or require in vitro production wherever feasible.

Purifying the Antibody

Whether the antibody comes from a bioreactor or ascites fluid, it needs to be separated from everything else in the mixture. The workhorse method is affinity chromatography using Protein A or Protein G, bacterial proteins that bind tightly to the constant region of immunoglobulin G (IgG). The crude supernatant is passed over a column packed with Protein A- or Protein G-coated beads; the antibody sticks, everything else washes through, and then the antibody is released with a change in pH.¹² Protein G has recently shown itself to be more versatile than once thought, purifying not just whole antibodies but also antibody fragments from both human and mouse origins in a single step.¹³ Membrane-based affinity chromatography using Protein A/G has also been developed for faster processing, producing IgG fractions clean enough to show no contaminant bands on gel electrophoresis.¹⁴

The Mouse Problem in Human Medicine

Hybridoma technology was built around mouse cells, and mouse antibodies work beautifully for research and diagnostics. The trouble starts when you inject a mouse antibody into a human patient. The human immune system recognizes it as foreign and mounts a response, producing what are called human anti-mouse antibodies, or HAMA. In a study of patients receiving murine antibody-drug conjugates at therapeutic doses, all ten developed elevated HAMA responses, typically within one to three weeks of treatment. By contrast, patients given tiny diagnostic doses of the same kind of antibody showed HAMA in only about 6% of cases.¹⁵ HAMA can neutralize the therapeutic antibody on repeat doses, cause allergic reactions, and even interfere with subsequent laboratory blood tests by cross-reacting with assay reagents.¹⁶

This limitation drove the development of several strategies to make mouse-derived antibodies more human-compatible. Chimeric antibodies replace the constant (non-binding) region of a mouse antibody with human sequences, keeping only the mouse variable region that contacts the target. Humanized antibodies go further, grafting just the small complementarity-determining regions (CDRs) responsible for antigen binding from the mouse antibody onto an otherwise fully human antibody framework. A structure- and docking-based CDR grafting approach has been used to produce humanized antibodies that retain virtually identical three-dimensional structure and binding affinity compared to the original mouse-derived version.¹⁷

The most aggressive solution skips mouse antibodies entirely. Trans-chromosomic mice have been engineered to carry the entire human immunoglobulin gene loci on a mouse-derived artificial chromosome, while their own mouse antibody genes are knocked out. When immunized, these mice produce fully human antibodies through the normal immune response. When their B cells are fused with myeloma cells in standard hybridoma fashion, the resulting hybridomas secrete fully human monoclonal antibodies ready for therapeutic development without any humanization engineering.¹⁸

Therapeutic Milestones

The first monoclonal antibody approved for human therapy was muromonab-CD3, marketed as OKT3 and approved by the FDA in 1986 for reversing acute organ transplant rejection. It worked by blocking all cytotoxic T-cell function, and clinical trials demonstrated that it reversed acute rejection episodes in kidney, liver, heart, and kidney-pancreas transplants, including cases that had resisted conventional treatment.¹⁹ OKT3 was eventually superseded by newer agents with better side-effect profiles, but it proved the concept that hybridoma-derived antibodies could work as drugs. Since then, monoclonal antibodies have become one of the fastest-growing drug classes, with applications spanning cancer (rituximab, trastuzumab, pembrolizumab), autoimmune disease (adalimumab, infliximab), infectious disease, and more.

Beyond the Mouse

Mice dominate hybridoma technology, but they are not the only option. Rabbits recognize epitopes and antigens that mice simply ignore, making rabbit monoclonal antibodies valuable for both research and potential therapy.²⁰ The stumbling block was that no rabbit equivalent of the mouse myeloma fusion partner existed. Researchers solved this by creating transgenic rabbits carrying oncogenes that predisposed them to developing plasmacytomas. From those tumors, stable cell lines were isolated that could serve as fusion partners, enabling the generation of rabbit-rabbit hybridomas that secrete rabbit monoclonal antibodies with the same stability and clonability as their mouse counterparts.²¹ Rabbit monoclonal antibodies are now common in diagnostic pathology, where their higher affinity often translates to crisper staining in tissue sections.

How Hybridoma Technology Compares to Newer Platforms

Hybridomas are no longer the only way to discover monoclonal antibodies. Phage display, for instance, skips animals altogether: libraries of antibody gene fragments are displayed on the surface of bacteriophages, and those that bind a target antigen are selected through repeated rounds of panning. The two approaches can even complement each other. When both methods were used in parallel against the same target (the receptor CXCR2), the hybridoma-derived antibody fully blocked the receptor’s natural ligands, while the phage-derived antibodies acted as allosteric antagonists recognizing entirely different epitopes. Neither approach alone captured the full diversity of useful antibodies.²²

Single B cell screening is another approach gaining ground, particularly for infectious disease applications where speed matters. Instead of fusing B cells with myeloma partners, individual B cells from an immunized animal or a recovering patient are isolated and their antibody genes are sequenced and cloned directly. Technological advances have increased the throughput and decreased the time required, making it possible to identify candidate antibodies within days rather than the weeks a hybridoma campaign typically takes.²³

Despite these alternatives, hybridoma technology persists for good reasons. It produces a living cell line that can be banked, shared, thawed, and scaled indefinitely. It does not require expensive sequencing infrastructure. And it has decades of validated protocols behind it, meaning almost any immunology lab in the world can run it with basic equipment. For applications where speed is less critical than long-term reproducibility, hybridomas remain a practical and cost-effective choice.

Patents and the Unusual History of Sharing

One reason hybridoma technology spread so rapidly through the scientific world is an unusual intellectual property story. Köhler and Milstein’s original 1975 paper was published without a patent. The UK Medical Research Council, which funded the work, did not file for patent protection, and the technology entered the public domain. This decision, sometimes described as a missed commercial opportunity and sometimes as a gift to global science, meant any lab could adopt the method freely. The subsequent rush of commercial interest in monoclonal antibodies led to a dense thicket of patents not on the core hybridoma technique itself but on specific antibodies, cell lines, screening methods, and humanization strategies built on top of it.²⁴ That interplay between open foundational technology and heavily patented applications continues to shape the antibody industry today.