Cancer immunotherapies are treatments that help a patient’s own immune system find and destroy cancer cells. Normally, the immune system might not recognize cancer cells as a threat, but these therapies condition or “train” immune cells to spot certain features – called antigens – that are found on cancer cells. Once trained, the immune cells work together to target and eliminate the cancer. There are different types of immune cells, each with their own job. Let’s look at some of these cell types and the role they play in immune system function.
First Line of Defense: Monocytes, Macrophages, and Dendritic Cells
Monocytes, macrophages, and dendritic cells are key immune cells that act as the body’s first line of defense, quickly detecting and neutralizing threats while also helping to activate the rest of the immune system for a more targeted response.
Monocytes travel through the bloodstream and are quick to respond to infections or injuries. When they reach areas where they are needed, they can change into macrophages.
Macrophages act like the body’s clean-up crew. When a macrophage detects something foreign, like bacteria and viruses, it surrounds and digests it using specialized enzymes. After breaking it down, the macrophage keeps a small piece of it—called an antigen—to show other immune cells what to look out for.
Dendritic cells are specialized immune cells that play a critical role in initiating and regulating immune responses. They’re mainly found in places where the body comes in contact with the outside world, such as the skin. Like macrophages, dendritic cells capture and break down invaders, then present antigens to other immune cells—especially T cells—to kick-start a broader immune response.1 Because of this, they’re sometimes called “professional antigen-presenting cells”.
Special Forces: Lymphocytes
Lymphocytes are produced by the bone marrow and play a key role in fighting infections, protecting against disease, and developing long-term immunity. If monocytes, macrophages, and dendritic cells are the first line of defense—acting quickly to spot and respond to threats—then lymphocytes can be thought of as the special forces of the immune system. Here’s why:
- They respond more specifically to threats after the first responders (like dendritic cells) alert them.
- They take a bit longer to activate but are highly targeted in their attack.
- They can form memory cells, allowing the immune system to respond faster if the same threat returns in the future—like remembering a past enemy.
While there are several types of lymphocytes, we’ll focus on one of the most common types: T cells.
T cells help destroy infected cells, cancer cells, and other cells identified as problematic to the immune system.2 T cells originate from the bone marrow and mature in the thymus, a small organ near the heart. Once fully developed, T cells can circulate throughout the body and gather in places like the spleen, tonsils, and lymph nodes, which are key parts of the immune system.
When macrophages and dendritic cells find something suspicious—like a virus, bacteria, or cancer cell—they bring the antigens to the lymph nodes and present them to the T cells. If the T cells recognize the antigen as a threat, they become “activated,” multiply, and go out to attack the dangerous cells.
The immune response depends on what kind of threat the antigen comes from. For example, bacteria usually cause a strong reaction, which is why an infected finger might become swollen and red—that’s your immune system in action. Viruses such as influenza, chickenpox, and norovirus often trigger pronounced immune responses as well, like congestion, sore throat, rash, and vomiting.
But cancer cells are trickier. Because they come from the body’s own cells, they often don’t look much different from normal cells. The immune system might ignore them, even when they seem a little off. On top of that, cancer cells can use special tactics to hide from the immune system. That’s why one of the biggest challenges in immunotherapy is getting the immune system to recognize the cancer cells and send T cells to destroy them.
With the ELIAS Cancer Immunotherapy (ECI®), the immune system is conditioned to recognize the individual’s unique cancer cells with personalized vaccines. However, vaccine stimulation alone most often is not enough to “activate” the T cells. With ECI®, the conditioned T cells are collected from the patient’s blood using apheresis, a process similar to dialysis. The T cells are then activated ex vivo and replicated into a large population before they are put back into that patient through an infusion. Once inside the body again, the activated T cells recognize the cancer cells and will seek them out and eliminate them.
Some T cells become “memory cells”, which “remember” the invader. If the same infection shows up again, these memory cells can quickly replicate—often stopping the infection before it causes major problems. That’s why people usually recover faster the second time they catch the same illness
A Well-Coordinated Defense System
The immune system functions like a highly trained army, constantly on alert to protect the body from harmful invaders, including cancer cells. Through complex teamwork between a variety of immune cells such as macrophages, dendritic cells and T cells, the body identifies and attacks cancer in a way that’s both precise and powerful. While the immune system’s natural defenses are impressive, immunotherapy offers a way to supercharge these defenses, training the body to fight cancer more effectively. As we continue to learn more about the immune system’s response to cancer, we’re unlocking new possibilities for treatments that may help patients achieve long-term remission and even a lasting immunity against cancer’s return.
Sources:
- Wculek, S.K., Cueto, F.J., Mujal, A.M. et al.Dendritic cells in cancer immunology and immunotherapy. Nat Rev Immunol 20, 7–24 (2020). https://doi.org/10.1038/s41577-019-0210-z
- Lymphocytes: Function, definition, Levels & Ranges. Cleveland Clinic. (2025, March 19). https://my.clevelandclinic.org/health/body/23342-lymphocytes