Cytokines and Their Side Effects
The immune system uses complex pathways to coordinate its response and protect the body from outside invaders. These include proteins and other molecules that help direct the immune response. Some of these can be used treatments to help the body kill cancer cells.
What are cytokines?
Cytokines are small proteins that help control the growth and activity of immune cells and blood cells. They are made by different types of white blood cells and are sometimes classified based which cells produce them:
- Lymphokines are made by lymphocytes
- Monokines are made by monocytes
How do cytokines work?
When released, cytokines signal the immune system to do its job. Cytokines affect the growth of all blood cells and other cells that help the body's immune and inflammation responses. They also help to boost anti-cancer activity by sending signals that can help make abnormal cells die and normal cells live longer.
Cytokines have multiple functions, based on their type:
- Interleukins act as chemical signals between white blood cells
- Interferons help the body resist virus infections and cancers
- Tumor necrosis factors signal immune cells to attack and kill cancer cells
- Growth factors support cell development and tissue repair
- Chemokines guide immune cells to where they¡¯re needed
Types of cytokines used in cancer treatment
Some cytokines can be made in a lab and are used to treat cancer. Others help prevent or manage chemotherapy side effects. Cytokines are injected, either under the skin, into a muscle, or into a vein.
The most common cytokines used in cancer care are interleukins and interferons. Depending on the type and stage of cancer, they can be used by themselves or with other treatments such as chemotherapy or other immunotherapy.
Interleukin-2 (IL-2)
Interleukins act as chemical signals between white blood cells. Interleukin-2 (IL-2) helps immune system cells grow and divide more quickly. A lab-made version of IL-2 called proleukin (aldesleukin) is approved to treat advanced kidney cancer and metastatic melanoma. IL-2 can be used as a single drug treatment for these cancers, or it can be combined with chemotherapy or with other cytokines such as interferon-alfa.
If IL-2 is given in high doses, it must be done in a hospital due to the risk of serious side effects.
Other interleukins, such as IL-7, IL-12, and IL-21, continue to be studied as stand-alone cancer treatments and as adjuvants, combined with other treatments.
Interferon-alpha (IFN-alfa)
Interferons help the body resist virus infections and cancers. The types of interferon (IFN) are named after the first 3 letters of the Greek alphabet:
- IFN-alfa
- IFN-beta
- IFN-gamma
Only IFN-alfa is used to treat cancer. It boosts the ability of certain immune cells to attack cancer cells. It may also slow the growth of cancer cells directly, as well as the blood vessels that tumors need to grow.
IFN-alfa can be used to treat these cancers:
- Hairy cell leukemia
- Chronic myelogenous leukemia (CML)
- Follicular non-Hodgkin lymphoma
- Cutaneous (skin) T-cell lymphoma
- Kidney cancer
- Melanoma
- Kaposi sarcoma
Growth factors
Growth factors are most commonly used to manage the side effects of cancer treatment. Certain types called colony-stimulating factors work by signaling immature white blood cells to grow and develop into mature cells. This can help the body better fight off active infection.
Tumor necrosis factor (TNF)
Tumor necrosis factor (TNF) signals immune cells to attack and kill cancer cells. It is also involved with inflammatory processes within the body. It¡¯s sometimes used to treat rheumatoid arthritis and is actively being studied as a treatment for some cancer types.
Side effects of cytokines
Side effects of cytokines differ from person to person and depend on the type of cytokine used. Some common side effects include:
- Chills
- Fever
- Fatigue
- Confusion
- Nausea and vomiting
- Diarrhea
- Neutropenia (low white blood counts)
- Increased risks of certain infections
- Hair loss
- Skin rashes
Less common and more serious side effects include:
- Low blood pressure
- Abnormal heartbeat
- Heart problems
- Chest pain
Side effects with interferon can be severe and can make treatment hard for many people to tolerate. Most side effects don¡¯t last long after the treatment stops, but fatigue can last longer. Other rare long-term effects include damage to nerves, including those in the brain and spinal cord.
Your cancer care team will watch you closely during treatment and will check you often. Side effects can and should be treated as early as possible. It¡¯s important to tell your cancer care team about any changes in how you feel or anything you notice that¡¯s new or unusual. Tell them right away so they can treat any problems and try to keep them from getting worse.
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- References
Developed by the ÁñÁ«ÊÓƵ medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
.American Society of Clinical Oncology (ASCO). What is immunotherapy? Accessed at cancer.net. Content is no longer available.
Gordon RA, Jackson N, Krause T, Mangan B, Martinez AL, Tipian CC. Immunotherapy. In Olsen MM, LeFebvre KB, Walker SL, Dunphy EP, eds. Chemotherapy and Immunotherapy Guidelines and Recommendations for Practice. 2nd ed. Pittsburgh, PA: Oncology Nursing Society; 2023:213-290.
Heimberger AB, Tripathi S, Platanias LC. Targeting cytokines and their pathways for the treatment of cancer. Cancers 2023. 15(21): 5224, https://doi.org/10.3390/cancers15215224
National Cancer Institute (NCI). Immune system modulators. Updated September 24, 2019. Accessed from https://www.cancer.gov/about-cancer/treatment/types/immunotherapy/cancer-treatment-vaccines on August 7, 2025.
Last Revised: July 7, 2025
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