Immunotherapy Basics

Immunotherapy is a type of biological therapy that utilizes a person's natural immune defense system to fight disease. Immunotherapy has been practiced for many years using vaccines to prevent certain types of diseases. Currently, there is a great deal of research being done on how immunotherapy can be used to treat cancer. Researchers have known for years that a person's immune system can have an affect on tumor cells if they are stimulated a specific way. Today, scientists are discovering ways in which immunotherapy can be used as a stand-alone treatment for cancer and a adjuvant (supplemental) treatment to make current cancer treatments more effective.

What Function Does the Immune System Serve?

The human immune system consists of many organs, cells, and chemicals with the purpose of protecting a person from infections, diseases and other foreign substances that may enter the body. Cells that make up the immune system travel throughout the body, including the bloodstream, searching for foreign substances that cause diseases. The goal of the immune system is to prevent these substances from doing harm to the body. In certain ways, it performs many functions for preventing cancer as well.

What is an Immune Response?

An immune response is triggered by a foreign substance that has invaded the body. These foreign substances are commonly referred to as antigens. The immune response usually leads to the immune system attacking these antigens with the intention of destroying them and anything they are attached to, such as other germs or even cancer cells.

The immune system is able to identify these foreign substances because bacteria, viruses, and other foreign substances have substances found on their surfaces which are not present inside the human body. The immune system is able to be alerted by these substances and they detect them as antigens. Cancer cells also have these antigens because their cell structure is not the same as most normal cells. The main problem, however, is that the immune system does a better job at recognizing attacking foreign substances than recognizing the cancer cells. This is because the differences between normal cells and tumor cells is often subtle. Consequently, the immune system will never attack the cancer cells.

The Uses of Immunotherapy to Treat Cancer

As mentioned above, cancer cells are usually ignored by the immune system because the cells of the immune system do not recognize the cancer as an immediate threat. Scientists are currently testing ways to help the immune system of a person with cancer to better recognize the presence of cancer and begin attacking those cells. There are several ways to do this, as researchers have discovered. The basic idea is to give the proper mission objectives to the T helper cells of the immune system so that they attack the cancer and continue to attack it until it is completely destroyed. This is called active immunotherapy, because the treatment given to the patient has a direct interaction with the body's immune system.

The other method of immunotherapy is to develop new ways to "create" antibodies and other types of cells that mimic the immune system of the human body. These synthesized cells are usually designed to attack cancer cells directly through the use of toxins and radioactive materials without interacting with the body's natural immune system. Due to its lack of interaction with the immune system, this is referred to as passive immunotherapy.

What are the Types of Immunotherapy?

Researchers have developed several methods of immunotherapy, most of which are still in the early clinical trial phases of development. Only a handful of immunotherapy treatments used to treat certain cancers have been approved by the FDA. The most common form of immunotherapy, monoclonal antibodies, has had a few of its uses approved by the FDA. Other immunotherapy methods, such as cancer vaccines, still have quite a lot of research ahead before they are proven effective and safe.

Monoclonal Antibodies:

This type of immunotherapy makes use of antibodies which have been synthesized inside a lab. These antibodies help recruit parts of the immune system to begin attacking the tumor cells inside a patient. Due to this fact, monoclonal antibody treatment is considered to be a passive immunotherapy.

Monoclonal antibody treatment has two methods of use. The first is naked monoclonal antibodies, which uses antibodies that have not been fitted with toxins or radioactive substances. In typical cases, the antibodies seek out the tumor and attach themselves to the cells of it. The immune system then sees the attached antibodies, which act as indicators, and the immune system begins to destroy the tumor cells. Naked monoclonal antibodies can also serve as "deactivation" cells. They do not interact with a person's immune system. Instead, these deactivation cells disable a vital function of the tumor, resulting in the death of the tumor cells.

The other use of monoclonal antibodies is called conjugated monoclonal antibodies. In this treatment, doctors fuse the antibodies with special drugs, such as toxins or radioactive substances. The antibodies are then programmed to seek out the tumor cells and attach themselves to it, and at the same time activating the drug. The effects of the drug then kill the tumor cells.

Toxic Targeted Therapy:

Targeted therapy is a type of treatment designed to destroy a tumor cell by exploiting a function vital for its survival. This therapy involves injecting antibodies into a patient attached with a special drug which destroys the cells. One example of this type of targeted therapy attacks the tumor cell's growth factors. These are structures on the tumor cells which allow it to grow and multiply much faster than normal cells. When the targeted therapy reaches the tumor cells, it administers the drug into these growth factors because the treatment itself is disguised as a growth receptor, a substance that helps to stimulate the growth of the cell.

Cancer Vaccines:

To understand how a cancer vaccine works, one must understand what a vaccine is. A vaccine is a substance that is usually injected into a healthy patient with the purpose of preventing a certain disease. The vaccine usually contains a portion of the disease which it is trying to prevent, whether it be bacteria or viruses. These disease causing microorganisms are first disabled or weakened in a lab so they do not cause the disease it intends to prevent. A person's immune system recognizes these disease causing microbes and begins to create antibodies that aid in preventing the disease. The person is now protected from contracting that disease because the immune system is equipped to stop it immediately.

Cancer vaccines work in a similar fashion, though they do not prevent disease. Rather, they help destroy cancer that already exists inside a patient. First, a doctor injects cancer cells into the patient. The cancer cells have been disabled in the lab to prevent them from growing and multiplying. They may have either come from the patient being treated (autologous) or another patient (allogeneic). These cancer cells may also be manually equipped with antigen substances to help gain the immune system's attention more easily. The immune system will then kill these cells and seek out other cells like it, including the patient's tumor.

There are several types of cancer vaccines, proving that cancer vaccine research is one of the most promising types of cancer research being done today. The following are the different cancer vaccines being developed today in clinical trial stages:

·         Tumor Cell Vaccines

·         Antigen Vaccines

·         Dendritic Cell Vaccines

·         Anti-idiotype Vaccines

·         DNA Vaccines

·         Vector-based Vaccines