How does immunotherapy work?

What does your immune system do?

Your body's immune system keeps intruders at bay. If they do manage to enter the body, it's the job of white blood cells to clear them out. There are many different types of white blood cells. They all have a different task. For example, there are 'gatekeepers' that look at all kinds of cells and molecules in your body to determine whether they are dangerous. When they track down an intruder, the gatekeepers send a signal to the other white blood cells to attack.

Innate and acquired

Part of your immune system works straight away, from birth. This part reacts quickly, but does not work very specifically. It includes, for example, the mucous membrane in your nose where bacteria and viruses are trapped. When your finger starts throbbing after you've had a nasty cut, that's also the innate immune system at play.

The learned part of your immune system is smarter and more specific. Every time you come across a new invader, such as a virus or bacteria, your learned or acquired immune system remembers how to recognize that invader. Two important types of white blood cells in the learned defense system are T cells and B cells. These help with remembering and destroying intruders, among other jobs. If you encounter the same intruder another time, it can be cleared up quickly and effectively, and you won't become ill.

Recognizing intruders

Sometimes the immune system doesn't work as it should. It might work against the wrong things, for example against your own cells. This is the case with diseases such as multiple sclerosis (MS) or arthritis. In the case of allergies, it reacts too strongly against intruders. The immune system is based on an important balance: it must recognize and clear invaders, but leave your body's own cells alone.

The immune system recognizes invaders with the help of a kind of 'flags' on the outside of all cells, called antigens. Every cell and every substance has a unique combination of flags on its surface: a skin cell, for example, has very different flags than a cell in the lungs. And all the cells of your own body have a 'this-is-me-flag'. These should be left alone.

Immune system and cancer

It may sound surprising, but cancer isn't actually an invader. A tumor starts when a normal cell in the body derails and continues to divide and grow unchecked. So when the immune system's gatekeepers come across a cancer cell, they often think they can let it through. Cancer cells also have all kinds of tricks to evade the immune system. That is why the immune system needs help in recognizing and destroying cancer cells: immunotherapy. This is a relatively new type of therapy that is used to treat some children and adults with cancer.

Antibody therapy

There are different types of immunotherapy. The most common forms are antibody therapy and cell therapy. Antibody therapy is a treatment with a drug containing artificially made antibodies. These antibodies act as small helpers that support the immune system. They are designed to very precisely recognize diseased cells or harmful proteins.

When the antibodies find a cancer cell, they attach to it, as if placing a flag on that cell. This makes it much easier for the immune system to recognize and specifically attack the cancer cell. In this way, the therapy helps the body clear the diseased cells.

An example of antibody immunotherapy is anti-GD2 therapy. This drug is used for children with neuroblastoma.

Treatment with bispecific antibodies

Another form of antibody therapy is treatment with bispecific antibodies. These are special antibodies that can recognize two different targets at the same time. They bind both to a marker on the cancer cell and to a marker on the body’s own immune cells. This brings the immune cell and the cancer cell close together, allowing the immune cells to attack the cancer cells directly. An example of this treatment is blinatumomab, a drug used for children with acute lymphoblastic leukemia (ALL).

Cell therapy

In cell therapy, the own immune cells are trained against the cancer. T cells, a type of white blood cell, are taken from the body and modified in the lab. The T-cells are programmed to specifically recognize and attack the cancer cells’ code. They are put back into the body with an IV drip, where they start to act the cancer cells.

In cell therapy, the immune system remembers the cancer cells’ signature code. This allows the immune system to attack again as soon as the cancer comes back. An example of cell therapy is CAR T-cell therapy. This is a form of immunotherapy given to some children with acute lymphoblastic leukemia (ALL).

Research

Immunotherapy is the newest kind of treatment for cancer. Immunotherapy is now part of the standard treatment for some children with neuroblastoma or ALL. Some children are cured thanks to immunotherapy. Scientists are carrying out a lot of research into immunotherapy, in the Princess Máxima Center and in the rest of the world. They are trying to make these treatments work better for the children who are already eligible for them - because the treatment does not yet work for all children. And in some children, the immunotherapy stops working after a while, for example if the cancer cells change their code. Scientists are also doing a lot of research to see how we can make immunotherapy work for increasingly many different forms of cancer.