Lymphocyte adoptive therapy represents a groundbreaking approach to fighting cancer by harnessing the body’s own immune cells. This treatment collects, strengthens, and multiplies a patient’s immune cells in a laboratory before returning them to attack tumors more effectively than they could on their own.
What Is Lymphocyte Adoptive Therapy?
Lymphocyte adoptive therapy is a type of immunotherapy, which means it uses the body’s immune system to fight cancer. Sometimes called adoptive cell therapy, adoptive immunotherapy, or immune cell therapy, this treatment focuses on using T cells, a type of white blood cell that plays a crucial role in identifying and destroying diseased cells[2]. The basic idea is simple but powerful: doctors remove immune cells from a patient’s body, grow millions more of them in a laboratory, and then give them back to the patient through an intravenous infusion. These reinforced cells are better equipped to recognize and eliminate cancer cells throughout the body.
This approach differs from other cancer treatments because it works with the patient’s own biology rather than introducing foreign substances. The immune cells used in the therapy come directly from the patient, which means they are specifically tailored to fight that individual’s cancer. This personalization is one of the therapy’s greatest strengths, as it can target cancer cells while potentially causing fewer side effects than traditional treatments like chemotherapy or radiation.
There are several distinct types of lymphocyte adoptive therapy currently being used or studied in clinical trials. The main categories include tumor-infiltrating lymphocyte (TIL) therapy, T cell receptor (TCR) therapy, and chimeric antigen receptor (CAR) T cell therapy[2]. Each approach has its own method of preparing and enhancing the immune cells, and each has shown promise in treating different types of cancer.
Types of Lymphocyte Adoptive Therapy
Tumor-Infiltrating Lymphocyte (TIL) Therapy
TIL therapy uses immune cells that have already found their way into a patient’s tumor. These tumor-infiltrating lymphocytes are special because they have already demonstrated the ability to recognize the cancer cells as foreign invaders[2]. However, there are usually not enough of these cells inside the tumor to destroy it completely, and the tumor may be releasing signals that suppress the immune system and prevent these cells from doing their job effectively.
The process begins with surgery to remove a piece of the patient’s tumor. Scientists then isolate the lymphocytes that are in or near the tumor tissue and test them in the laboratory to identify which ones react most strongly to the tumor cells[2]. The selected lymphocytes are then treated with special substances that help them multiply rapidly, growing from perhaps a few million cells to billions over the course of two to eight weeks[2]. Before the cells are returned to the patient, the patient typically receives chemotherapy and sometimes radiation therapy to temporarily reduce their existing immune cells. This step, while it may seem counterintuitive, actually helps the transferred cells work more effectively by making room for them and reducing competition.
In February 2024, the U.S. Food and Drug Administration approved a TIL therapy called lifileucel (Amtagvi) for treating advanced melanoma, a serious form of skin cancer[2]. This was a historic moment because lifileucel became the first cell therapy approved for any solid tumor. Research has shown that TIL therapy can produce objective cancer regression in approximately fifty percent of patients with metastatic melanoma who have not responded to other treatments[3]. TIL therapy has also shown promising results in clinical trials for other cancers, including cervical squamous cell carcinoma and cholangiocarcinoma, although it remains experimental for these conditions[2].
T Cell Receptor (TCR) Therapy
Not all cancer patients have T cells that naturally recognize their tumors, or those cells may not be strong enough to be useful in therapy. For these patients, doctors developed TCR therapy, which involves genetically modifying the patient’s T cells to give them new capabilities[4]. In this approach, scientists take T cells from the patient’s blood and introduce genes that code for a T cell receptor designed to recognize specific cancer antigens. An antigen is a marker or protein found on the surface of cells that the immune system can recognize.
The engineered T cell receptors allow the modified T cells to identify and attack cancer cells by recognizing antigens that are presented through a system called the major histocompatibility complex (MHC)[4]. This system is like a display case on the cell surface that shows samples of proteins from inside the cell. By equipping T cells with receptors specifically designed to recognize cancer-related antigens, doctors can create an army of cells programmed to hunt down tumor cells. The advantage of this approach is that doctors can choose the most effective target for each patient’s specific type of cancer and design the receptor accordingly.
Chimeric Antigen Receptor (CAR) T Cell Therapy
CAR T cell therapy represents another advancement in genetically engineering immune cells to fight cancer. Like TCR therapy, CAR T cell therapy involves collecting T cells from a patient’s blood and modifying them in the laboratory. However, CAR T cells are equipped with a synthetic receptor called a chimeric antigen receptor[2]. The word “chimeric” refers to something made from parts of different sources, and these receptors combine elements from different proteins to create something new.
A major advantage of CAR T cells is that they can recognize and bind to cancer cells without needing the antigens to be presented through the MHC system[4]. This makes them effective against a broader range of cancer cells, including those that might otherwise hide from the immune system. However, CAR T cells can only target antigens that are naturally expressed on the cell surface, which limits the number of potential targets compared to TCR therapy.
As of 2024, six CAR T cell therapies have received approval from the U.S. Food and Drug Administration for treating blood cancers. These include axicabtagene ciloleucel (Yescarta), brexucabtagene autoleucel (Tecartus), ciltacabtagene autoleucel (Carvykti), idecabtagene vicleucel (Abecma), lisocabtagene maraleucel (Breyanzi), and tisagenlecleucel (Kymriah)[2]. These treatments have shown particularly impressive results in treating certain types of leukemia and lymphoma. Research is ongoing to extend the use of CAR T cell therapy to solid tumors such as breast cancer and brain tumors, though these applications remain experimental.
How Lymphocyte Adoptive Therapy Works in the Body
Understanding how lymphocyte adoptive therapy works requires knowing a bit about how the immune system normally fights disease. T cells are specialized white blood cells that patrol the body looking for signs of infection or abnormal cells. When a T cell encounters a cell displaying suspicious antigens, it can bind to that cell and release toxic substances that destroy it. This process is highly specific, meaning each T cell is programmed to recognize particular antigens.
In cancer, this natural defense system often fails for several reasons. The tumor may not display enough recognizable antigens, or it may actively suppress the immune response by releasing chemicals that shut down T cell activity[2]. Additionally, even if some T cells do recognize the cancer, there may simply not be enough of them to overcome the rapidly growing tumor. The tumor’s environment can also be hostile to immune cells, making it difficult for them to survive and function properly.
Lymphocyte adoptive therapy addresses these problems by collecting the patient’s most effective anti-tumor T cells, multiplying them to enormous numbers in a controlled laboratory environment, and sometimes enhancing them through genetic engineering. When billions of these optimized cells are infused back into the patient, they can overwhelm the tumor’s defenses through sheer numbers and improved capabilities[3]. The preparatory chemotherapy or radiation that patients receive before the cell infusion helps by clearing out other immune cells and creating a favorable environment where the transferred cells can thrive and multiply further.
After infusion, the transferred T cells circulate through the bloodstream, seeking out cancer cells wherever they may be hiding in the body. Unlike surgery or radiation, which can only treat cancer in specific locations, adoptive cell therapy can potentially reach metastatic cancer that has spread to multiple sites. When the engineered or selected T cells find their targets, they attach to the cancer cells and kill them through various mechanisms, including releasing toxic proteins or triggering the cancer cells to self-destruct.
Cancers Treated with Lymphocyte Adoptive Therapy
Lymphocyte adoptive therapy has shown the most dramatic success in treating blood cancers, particularly certain types of leukemia and lymphoma. The six approved CAR T cell therapies are all used for blood cancers because these cancers have characteristics that make them especially vulnerable to this approach[2]. Blood cancer cells circulate throughout the body and often express specific antigens, such as CD19, that are ideal targets for CAR T cells. Clinical trials have demonstrated that CAR T cell therapy targeting CD19 can lead to complete remission in patients with relapsed and refractory leukemia who had run out of other treatment options.
For solid tumors, TIL therapy has emerged as the most successful approach so far. The approval of lifileucel for advanced melanoma marked a turning point, as melanoma had long been considered one of the deadliest forms of skin cancer with limited treatment options for advanced cases[2]. Studies from the National Cancer Institute showed that TIL therapy could mediate objective cancer regression in about half of patients with metastatic melanoma, with some patients experiencing complete and durable responses[3].
Beyond melanoma and blood cancers, researchers are actively investigating lymphocyte adoptive therapy for many other cancer types. Clinical trials are testing these approaches in breast cancer, brain tumors, ovarian cancer, and lung cancer, among others[2]. However, solid tumors present unique challenges that make them harder to treat than blood cancers. They create physical barriers that immune cells must penetrate, they often have heterogeneous populations of cancer cells with varying antigens, and they generate an immunosuppressive microenvironment that can disable attacking T cells.
Post-transplant lymphomas, which can develop in patients who have received organ transplants and are taking immunosuppressive drugs, represent another area where adoptive cell therapy has shown effectiveness. Using donor lymphocytes for this purpose has proven to be an effective treatment for these immunosuppressed patients[5].
Advantages of Lymphocyte Adoptive Therapy
Lymphocyte adoptive therapy offers several important advantages over other forms of cancer treatment. One key benefit is that doctors can grow massive numbers of tumor-specific T cells in the laboratory and select for those with the highest activity against the cancer[3]. This ability to expand and select the most effective cells means that patients receive an optimized army of cancer fighters rather than relying solely on whatever their body can naturally produce.
Another advantage is the potential for personalization. Each patient’s therapy is created using their own cells and tailored to target their specific cancer. In the case of TIL therapy, the cells naturally recognize the patient’s particular tumor antigens. With engineered approaches like TCR and CAR T cell therapy, doctors can design receptors to target antigens that are most relevant to that patient’s cancer type. This level of customization is difficult or impossible to achieve with standard chemotherapy drugs, which affect all rapidly dividing cells whether cancerous or healthy.
The ability to manipulate the patient’s body before cell infusion represents another strategic advantage. By administering chemotherapy or radiation before transferring the T cells, doctors create an environment that is more favorable for the therapy to work[3]. This preparatory treatment, called lymphodepletion, reduces competing immune cells and may also eliminate regulatory cells that would otherwise suppress the anti-tumor response.
Lymphocyte adoptive therapy can also create lasting immunity in some patients. Unlike chemotherapy, which stops working once treatment ends, transferred T cells can persist in the body for months or years, continuing to patrol for cancer cells. Some patients who achieve complete remission with adoptive cell therapy remain cancer-free for extended periods, suggesting that the therapy may provide durable protection.
The Treatment Process
The journey through lymphocyte adoptive therapy involves multiple steps that typically span several weeks or months. For TIL therapy, the process begins with surgery to remove tumor tissue. This procedure requires careful planning to ensure that enough viable tumor can be obtained to harvest lymphocytes. The surgical specimen is then transported to a specialized laboratory, where technicians work to isolate and identify the T cells that have infiltrated the tumor.
For CAR T cell and TCR therapies, the starting point is a procedure called leukapheresis, where blood is drawn from the patient and passed through a machine that separates out the white blood cells, including T cells. The remaining blood components are returned to the patient. This collected cell sample is then sent to a manufacturing facility where the genetic engineering takes place.
During the cell manufacturing period, which can last from two to eight weeks, the patient may undergo various tests and preparations for treatment[2]. As the cells near completion in the laboratory, the patient receives lymphodepleting chemotherapy and possibly radiation therapy. This preparatory treatment is carefully timed to occur shortly before the cell infusion.
The actual infusion of the manufactured cells is relatively straightforward and similar to receiving a blood transfusion. The cells are delivered through an intravenous line, usually over a period of thirty minutes to several hours. Following the infusion, many patients receive additional treatments to support the transferred cells. For TIL therapy, this often includes high-dose interleukin-2, a growth factor that helps T cells survive and multiply[2].
After the infusion, patients are monitored closely for several days or weeks. They may need to stay in the hospital or visit frequently for observation and management of side effects. Healthcare teams watch for signs that the therapy is working, such as shrinking tumors, as well as for potential complications that require intervention.
Understanding Potential Side Effects
Like all cancer treatments, lymphocyte adoptive therapy can cause side effects, some of which can be serious. The preparatory chemotherapy and radiation that patients receive before the cell infusion can cause temporary side effects such as low blood cell counts, increased infection risk, fatigue, nausea, and hair loss. These effects are similar to those experienced with conventional chemotherapy but are usually temporary as the bone marrow recovers.
The transferred T cells themselves can trigger immune-related side effects. Because these cells are highly active and can cause significant inflammation as they attack cancer cells, patients may experience fever, chills, low blood pressure, and flu-like symptoms. These reactions are often signs that the therapy is working, but they require careful medical monitoring and management.
High-dose interleukin-2, which is often given after TIL therapy to help the transferred cells survive and multiply, can cause its own set of side effects including fluid retention, low blood pressure, kidney problems, and confusion[2]. Because of these potential complications, patients receiving interleukin-2 typically need to be hospitalized in intensive care units where they can be closely monitored.
Some patients experience more severe immune reactions. When CAR T cells become highly activated and release large amounts of inflammatory chemicals all at once, this can lead to a condition called cytokine release syndrome. Symptoms can range from mild fever to life-threatening complications affecting multiple organs. Another potential complication is neurotoxicity, where inflammation affects the nervous system and causes confusion, difficulty speaking, or seizures.
Because adoptive cell therapy suppresses the patient’s normal immune system both through the preparatory chemotherapy and through the overwhelming presence of the transferred cells, patients face an increased risk of infections for weeks or months after treatment. They may need to take antibiotics, antifungal medications, or antiviral drugs as preventive measures. Some patients may require additional treatments to support their blood counts or immune function during recovery.
Current Limitations and Challenges
Despite the impressive successes of lymphocyte adoptive therapy, significant challenges remain. One major limitation is that the therapy does not work for all patients. Even in melanoma, where TIL therapy has shown the best results in solid tumors, only about half of patients experience objective responses[3]. Scientists are still working to understand why some patients respond well while others do not, and how to predict which patients are most likely to benefit.
The complexity and cost of manufacturing adoptive cell therapies present another significant barrier. The process of collecting cells, growing them in the laboratory, and in some cases genetically engineering them requires sophisticated facilities, specialized equipment, and highly trained personnel. Each patient’s therapy must be individually manufactured, which is time-consuming and expensive. This manufacturing complexity can limit access to these treatments and make them difficult to scale up to treat large numbers of patients.
For solid tumors, additional biological challenges make adoptive cell therapy less effective than it is for blood cancers. Solid tumors create dense masses of tissue that can be difficult for T cells to penetrate. They also develop microenvironments that actively suppress immune function by releasing inhibitory chemicals, depleting nutrients that T cells need, and recruiting other cells that block immune responses. Even when T cells successfully infiltrate a tumor, they may become exhausted and lose their ability to kill cancer cells.
Tumor heterogeneity poses another problem. Unlike some blood cancers where most or all cancer cells express the same target antigen, solid tumors often contain diverse populations of cancer cells with different antigen profiles. If the transferred T cells only recognize one antigen and some tumor cells do not express it, those cells can escape attack and cause the cancer to recur. Cancer cells can also lose or modify their surface antigens over time as a way of evading the immune system.
The requirement for preparatory chemotherapy and the toxicity of supporting treatments like high-dose interleukin-2 mean that not all patients are healthy enough to undergo adoptive cell therapy. Patients must have adequate organ function and overall health to withstand the intensive treatment process. This requirement can exclude some patients who might otherwise benefit from the therapy.
Promising Future Directions
Researchers are actively working on strategies to overcome the current limitations of lymphocyte adoptive therapy and extend its benefits to more patients and more types of cancer. One approach involves combining adoptive cell therapy with other treatments. Clinical trials are testing combinations with checkpoint inhibitors, drugs that block proteins that suppress immune responses. The idea is that checkpoint inhibitors might help the transferred T cells remain active longer and overcome the immunosuppressive tumor environment.
Scientists are also developing more sophisticated ways to engineer T cells. Next-generation CAR T cells are being designed with multiple targeting domains that can recognize several different antigens simultaneously, making it harder for cancer cells to escape by losing a single target. Other engineering strategies focus on equipping T cells with additional capabilities, such as resistance to the suppressive signals in the tumor microenvironment or the ability to recruit other immune cells to help fight the cancer.
Improvements in manufacturing processes may help make these therapies more accessible and affordable. Automation and standardization of cell production could reduce costs and increase capacity. Some researchers are exploring the possibility of using donor cells rather than the patient’s own cells, which could allow for “off-the-shelf” therapies that do not require individual manufacturing for each patient. While this approach introduces the risk of rejection and graft-versus-host disease, it could dramatically reduce the time and cost associated with treatment.
Novel culture techniques and genetic modifications are being developed to produce T cells that are more potent and longer-lasting. Scientists are learning how to select or engineer T cells that have characteristics associated with better clinical outcomes, such as the ability to self-renew and persist in the body for extended periods. Research into the tumor microenvironment is revealing new targets that could be manipulated to make tumors more vulnerable to immune attack.
The field is also exploring the use of other types of immune cells beyond T cells. Natural killer (NK) cells, another type of lymphocyte, are being investigated for their potential in adoptive cell therapy. These cells have different mechanisms for recognizing and killing abnormal cells and might offer advantages in certain situations.