Immunotherapy is the treatment of disease by inducing, enhancing or suppressing an immune response. The active agents of immunotherapy are collectively called immunomodulators.
Types of immunotherapy:
1. Active immunotherapies: immunotherapies designed to elicit or amplify an immune response are called activation immunotherapies.
2. Suppression immunotherapies: immunotherapies designed to reduce, suppress or more appropriately direct an existing immune response, as in cases of autoimmunity or allergy are called suppression immunotherapies.
Justify the use of monoclonal antibodies in cancer therapy.
Two types of monoclonal antibodies are used in cancer treatments:
- Naked monoclonal antibodies: Naked monoclonal antibodies are those without any drug or radioactive material attached to them. Naked MAbs are the most commonly used MAbs at this time. Although they all work by attaching themselves to specific antigens, they can be helpful in different ways. Some naked MAbs attach to cancer cells to act as a maker for the body’s immune system to destroy them.
- Conjugated monoclonal antibodies: Conjugated monoclonal antibodies are those joined to a chemotherapy drug, radioactive particle or a toxin (a substance that poisons cells). Conjugated MAbs are monoclonal antibodies that are attached to drugs, toxins or radioactive substances. The MAbs are used as homing devices to take these substances directly to the cancer cells. The MAbs circulates in the body until it can find and hook onto the target antigen. It then delivers the toxic where it is needed most. Conjugated MAbs are also sometimes referred to as tagged, labeled or loaded antibodies. They can be divided into following groups: a. Radiolabeled antibodies: MAbs with radioactive particles attached are referred to as radiolabeled and therapy with type of antibody is known as Radioimmunotherapy (RIT). Two radiolabeled antibodies have been approved to treat cancer. Ibritumomab tiuxetan (Zevalin) delivers radioactivity directly to cancerous B lymphocytes. It is used to treat B cell non Hodgkin lymphoma that has not responded to standard treatment. Tositumomab (Bexxar) is used to treat certain types of non-Hodgkin lymphoma that no longer respond to rituximab (Rituxan) or chemotherapy. b. Chemolabeled antibodies: MAbs with chemotherapy drugs attached are often referred to as chemolabeled. These are being studied and are available in the United States only through clinical trials at this time. None have been approved by the FDA as of mid-2009.
Cytokines are chemicals made by immune system cells. They have a crucial role in regulating the growth and activity of other immune system cells and blood cells. At this time, cytokines are often used in cancer treatment to lessen the side effects of other treatments such as chemotherapy. Cytokines are given as injections either under the skin into muscle or into a vein.
The most common ones are discussed below:
1. Interleukins: Interleukins are a group of cytokines that act as chemical signals between white blood cells. When interleikin-2 (IL-2) was approved the FDA in 1992 to treat advanced kidney cancer, it became the first true immunotherapy approved for use alone in treating cancer. Since that time, it has also been approved to treat people with metastatic melanoma. Other interleukins, such as il-7, IL-12 and IL 21 are now being studies for use against cancer too, both as adjuvants and as standalone agents.
2. Interferons: This family of cytokines, first discovered in the late 1950s, helps the body6 resist virus infections and cancers. The interferons are of 3 types- IFN-alfa, IFN-beta and IFN gamma. Although all 3 types of interferon are FDA approved to treat health conditions. The FDA has approved IFN-alfa for use against these cancers:
a. Hairy cell leukemia
b. Chronic myelogenous leukemia
c. Follicular non-Hodgkin lymphoma
d. Cutaneous (affecting the skin) T- cell lymphoma
e. Kidney cancer
g. Kaposi Sarcoma