What is immunotherapy?

The immune system protects the body against illness and infection. Immunotherapies are treatments that use the immune system to find and attack cancer cells.

There are different types of immunotherapy. Each one uses the immune system in a different way.

Some types of immunotherapy are also a targeted therapy.

If you know the name of the drug you are looking for, you can use our list of treatments to find it. This gives more information about:

  • what each treatment is
  • how it is given
  • possible side effects.

Checkpoint inhibitors

Checkpoint inhibitors affect a type of white blood cell called a lymphocyte. Lymphocytes are an important part of the immune system. When they are active, lymphocytes can attack another cell such as a cancer cell. But if they receive a certain signal from the other cell, they switch off (become inactive) and do not attack it.

Checkpoint inhibitors block the signals that switch off lymphocytes. They do this by attaching to either the cancer cell or the lymphocyte. This means the lymphocyte stays active and can attack the cancer cell.

Immune system modulators

Immune system modulators are immunotherapy drugs. They help the immune system attack and destroy cancer cells.

They are given as tablets. Types of immune system modulator include:

Other immune system modulators include artificial versions of proteins called interferon and interleukin. These proteins are normally made naturally in the body. They help control how the immune system works. Interferon and interleukin are given by injection. They are not used very often, as newer drugs have become available.

BCG for bladder cancer

Another type of immune system modulator is BCG. BCG is a type of bacteria which can cause tuberculosis (TB). It can be weakened, so that it is not harmful, and used as a treatment for bladder cancer. It is given directly into the bladder to stimulate the immune system to attack cancer cells. This is called intravesical immunotherapy.

Virus therapy to treat cancer

Virus therapy uses a virus that has been made or changed in a laboratory. The virus finds and infects the cancer cells. This treatment also trains the immune system to find and attack cancer cells.

A virus therapy called T-VEC (Imlygic®) is sometimes used to treat melanoma that has come back in the same area. Other types of cancer may be treated with virus therapies as part of a research trial (clinical trial).

Monoclonal antibodies

All cells have receptors on their surface. Receptors help cells send or receive signals. A receptor is a bit like a lock. Only the right key fits the lock. Another cell or substance can only connect to the receptor if it is the right fit.

Monoclonal antibodies are made so they can only connect to one type of receptor. Most monoclonal antibodies target receptors that are mainly found on cancer cells. Some target receptors that are found on other cells in the body.

By connecting to the cell’s receptor, monoclonal antibody immunotherapies can help the body’s immune system by:

  • blocking signals that stop white blood cells attacking cancer cells (also called a checkpoint inhibitor)
  • connecting to cancer cells to help the immune system find and attack them.

Cancer vaccines

Vaccines train the immune system to find and attack certain types of abnormal cells. They are commonly used to protect us from infections such as the flu, mumps or measles. Sometimes vaccines can be used to train the immune system to find and attack cancer cells.

A vaccine that prevents the infection tuberculosis (TB) is sometimes used after treatment for non-invasive bladder cancer. This is called BCG treatment.

Scientists and doctors are researching ways to make new vaccines that target cancer cells. They may be used to treat several types of cancer. They are usually only available as part of a research trial (clinical trial).

Adoptive cell transfer and CAR-T therapy

Adoptive cell transfer and T-cell therapy use a person’s own white blood cells to find and destroy cancer cells. White blood cells usually fight infection.

Some white blood cells are collected from the body. Scientists then either:

  • choose the cells that are naturally best at recognising cancer cells
  • change cells to make them better at recognising cancer cells.

More of these cells are then grown in the laboratory. They are given back into the bloodstream to find and attack cancer cells.

There are different types of adoptive cell transfer. For example, T-cell therapy or CAR T-cell therapy uses white blood cells called T cells. These treatments are in the very early stages of development and are only available as part of a research trial (clinical trial).

Side effects of immunotherapy

Immunotherapy causes the immune system to become more active. That means it is better at finding and attacking cancer cells. But immunotherapy can also cause unwanted effects. These are very different to the side effects of other cancer treatments, such as chemotherapy or radiotherapy.

For example, checkpoint inhibitors can make the immune system too active. This causes inflammation in the body. The most common parts of the body they affect are the:

  • skin – causing a rash, itching or changes in skin colour
  • glands in the body that make hormones – causing problems such as sweating, weight changes, feeling more hungry or thirsty, passing more urine (peeing), loss of sex drive, feeling tired (fatigue) or headaches
  • bowels – causing diarrhoea or tummy pain
  • joints – causing pain and swelling.

More rarely, these drugs cause problems in other places, such as:

  • the liver
  • the lungs
  • the heart
  • the nerves
  • the brain
  • other organs.

Sometimes this type of side effect can start weeks or months after you finish treatment. It can also appear more than a year after treatment ends.

Some people have very few side effects, but the side effects of checkpoint inhibitors can be serious.

Date reviewed

Reviewed: 01 August 2022
Next review: 01 August 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

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