Your immune system can recognize melanoma but often times the response is not strong enough to find and destroy the tumor. Interferon is a small protein that acts directly on the melanoma cells to increase certain proteins that the immune system needs in order to shrink the tumors. Interferon also stimulates or ‘alerts’ the immune system. Thus, interferon makes your tumor more visible to an alerted immune system.

Basically, since viruses have unique proteins that they use to invade and multiply, one could look in the tumor for the presence of these specific proteins or the genes that encode them.There are several ways to do this now and these methods are being used to probe various cancers.

Antibodies are proteins produced by the B cells of the immune system that are capable of binding to other proteins. Each new B cell generated by your body has a unique antibody due to genetic recombination.There are millions of different antibodies. When the immune system sees a new antigen from a virus, bacteria, or tumor, it screens these different antibodies for reactivity against the antigen. Once an antibody that binds to the antigen is found, the B cell that produces it expands and grows exponentially leading to millions of B cells that produce that antibody. Thus, your body can become flooded with the antibodies. Antibodies have multiple functions when they bind to tumor cells. Antibodies can activate what are called natural killer cells, which directly kill tumors coated with antibodies. Antibodies can be synthesized artificially and sold for injection into cancer patients. The antibody Herceptin for the treatment of HER-2/neu breast cancer is a good example.

BCG is a vaccine used for preventing tuberculosis in several countries. It is not used in the USA because the protective effects in North America have not been that compelling. It is a weakened form of the bacterium M. bovis, the agent that causes tuberculosis in cattle. It is closely related to M. tuberculosis, the agent that causes tuberculosis in humans. It is used to treat some forms of bladder cancer. It is directly injected into the bladder. The mechanisms by which BCG works remain somewhat of a mystery, but it is thought that the generation of an immune response to BCG in the bladder leads to secondary anti-tumor immunity which shrinks residual tumor deposits following surgery.

BCG also contains a number of danger signals that the innate (i.e. non-adaptive) immune system responds to vigorously. Because of this property it is often used as a cancer vaccine adjuvant (i.e. something that enhances immune responses).

The T cell is one of the two major cell types of the ‘adaptive’ immune system. The other is the antibody-producing B cell. Adaptive means that the immune response adapts to the specific threat such as a virus. T cells express a cell surface protein called the T cell receptor (TCR). The TCR for each T cell is different due to genetic recombination. There are millions of different TCRs. When the immune system sees a new antigen from a virus, bacteria, or tumor, it screens these different TCRs for reactivity against the antigen. Once a T cell(s) responds, it expands and grows exponentially leading to millions of T cells that recognize that specific antigen, hence the term adaptive.There are two major kinds of T cells, the CD4 helper T cell and the CD8 cytotoxic T cell. The CD4 helper T cell is the central orchestrator of the immune response and stimulates antibody production and CD8 cytotoxic T cell activation. CD4 T cells recognize antigens released by tumor cells. These antigens are picked up by what are called antigen presenting cells (APCs). These APCs break the protein antigens into fragments called peptides. These peptides are then presented to the CD4 helper T cells attached to specialized proteins called HLA-class II molecules. Once activated, CD4 helper T cells activate other immune cells by releasing a number of proteins into tissues and the blood. In contrast to the CD4 helper T cell, the CD8 are cytotoxic which means that they directly kill the cells presenting tumor or virus antigens. They recognize peptides presented by HLA class I molecules, which are on all cells in the body.

Vaccines stimulate antigen-specific T cells and antibody responses. An antigen is a protein, fat, or carbohydrate that is recognized by the immune system as foreign. Tumor cells produce many antigens rarely encountered in the body and consider these antigens foreign. There are two major kinds of T cells, the CD4 helper T cell and the CD8 cytotoxic T cell. The CD4 T cell is the central orchestrator of the immune response and stimulates antibody production and CD8 cytotoxic T cell activation. CD4 T cells recognize antigens released by tumor cells. The CD8 cytotoxic T cell directly kills tumor cells that display antigens not ordinarily expressed in other parts of the body. Antibodies, produced by B cells, can bind to the surface of the tumor leading toactivation of a wide variety of tumor destructive mechanisms. The unique feature of the adaptive immune system is memory. So, when vaccine generates the immune response, the immune system remembers this and can fight tumors that emerge later in life. Thus, vaccines can be used in preventing cancer too, in much the same way that vaccines can stimulate immunity against the polio virus providing lasting protection from contracting polio.

A number of different ways have been identified in recent years. Some of the strategies with explanations are listed below.

a. Recruitment of immune suppressor cells:The immune system has specialized cells that work to control immune responses so they do not become toxic to the body. Tumor cells can secrete various substances that can attract in a lot of immune suppressor cells. Once inside the tumors, these suppressor cells can inhibit the functions of anti-tumor cytotoxic T cells as well as other immune cells that could contribute to tumor cell death.

b. Loss of antigen: The adaptive immune response to tumors is specific for various protein and carbohydrate antigens. Once the immune response is initiated against a tumor, variant tumor cells that do not express the antigens can continue to grow. After some time, the tumor will no longer express the antigens that the immune system is capable of seeing.

c. Loss of HLA molecules: HLA molecules are specialized proteins expressed by all cells. They help to present tumor antigens to the immune system. For example, if your upper airway cells are infected with the flu virus, the HLA molecules will anchor the flu proteins to the cell surface making them visible targets for incoming CD8 cytotoxic cells. The cytotoxic T cells will then destroy those infected cells so that they do not continue to produce virus. The body heals itself by replacing those dead infected cells with fresh uninfected cells.

d. Production of immune suppressive cytokines: Tumors cells can be induced by the immune system to produce one or more of a few immune suppressive cytokines. These cytokines can directly prevent T cell activation.