Skip to Content



Peter J. Delves

, PhD, University College London, London, UK

Last full review/revision Apr 2020| Content last modified Apr 2020

Immunotherapy is the use of drugs that mimic or modify components of the immune system (such as tumor antigens and immune checkpoints—see also Overview of the Immune System) to fight disease. Immunotherapy is rapidly evolving, especially in the field of cancer treatment.

Several types (classes) of immunotherapeutic drugs have been developed. Some of the most common classes are

  • Cytokines and cytokine receptors
  • Fusion proteins
  • Monoclonal antibodies

Cytokines and Cytokine Receptors

Cytokines are the chemical messengers of the immune system. White blood cells and certain other cells of the immune system produce cytokines when they detect a foreign substance (antigen). Examples of cytokines include interferons and interleukins. Cytokines transmit their message by attaching to specific molecules called receptors on the surface of another cell. Cytokines and their receptors are a bit like a key and lock. Different cytokines have different receptors.

Cytokines or their receptors can be produced in a laboratory. When given to a person, the artificial cytokine or cytokine receptor can be used to modify the person's natural immune response and treat many diseases.

Cytokines or cytokine receptors are used to do the following:

Fusion Proteins

Fusion proteins are compounds that are produced in the laboratory and combine or "fuse" two different proteins with desirable immune-modifying and disease-fighting traits to form a single drug. When given to a person, the newly created fusion protein can be used to modify the natural immune response and treat many diseases. An example of a fusion protein is the drug etanercept, which fuses a cytokine receptor with an antibody.

Fusion proteins are used to do the following:

Monoclonal Antibodies

Monoclonal antibodies (mAbs) are antibodies that are produced in a laboratory from living cells that have been altered to produce the desired antibody. When injected into a person's bloodstream, they act like the antibodies produced in the human body. Monoclonal antibodies are usually designed to attack cancer cells or the substances that cause inflammation in disorders such as rheumatoid arthritis.

Monoclonal antibodies are used to do the following:

Because monoclonal antibodies are often used to suppress the immune system, they can have significant side effects such as an increased risk of infection or cancer and can also result in autoimmune disorders.

Drugs Mentioned In This Article

Generic Name Select Brand Names
etanercept ENBREL

Copyright © 2022 Merck & Co., Inc., known as MSD outside of the US, Kenilworth, New Jersey, USA. All rights reserved. Merck Manual Disclaimer