Immunotherapy

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

The term immunotherapy incorporates an array of strategies of treatment based upon the concept of modulating the immune system to achieve a prophylactic and/or therapeutic goal.

Immunotherapy can be "either active or passive. Active immunotherapy involves setting an immune response in the cancer patient to fight cancer cells. In passive immunotherapy, immune molecules are given to patients who do not produce them on their own. Both approaches can be specific or nonspecific."

Activation

Cancer

Cancer immunotherapy attempts to stimulate the immune system to reject and destroy tumors. BCG immunotherapy for early stage (non-invasive) bladder cancer utilizes instillation of attenuated live bacteria into the bladder, and is effective in preventing recurrence in up to 2/3 of cases. Topical immunotherapy utilizes an immune enhancement cream (imiquimod) which is an interferon producer causing the patients own killer T cells to destroy warts, actinic keratoses, basal cell cancer, squamous cell cancer, cutaneous lymphoma, and superficial malignant melanoma. Injection immunotherapy uses mumps, candida or trichophytin antigen injections to treat warts (HPV induced tumors).

Dendritic cell based immunotherapy

This utilizes dendritic cells to activate a cytotoxic response towards an antigen. Dendritic cells, an antigen presenting cell, are harvested from a patient. These cells are then either pulsed with an antigen or transfected with a viral vector. The activated dendritic cells are then placed back into the patient; these cells then present the antigens to effector lymphocytes (CD4+ T cells, CD8+ T cells, and in specialised dendritic cells, B cells also). This intitiates a cytotoxic response to occur against these antigens and anything that may present these antigens. One use for this therapy is in cancer immunotherapy. Tumor Antigens are presented to dendritic cells which cause the immune system to target these antigens, which are often expressed on cancerous cells.

T cell based adoptive immunotherapy

This therapy uses T cell-based cytotoxic responses to attack cancer. In brief, T cells that have a natural or genetically engineered reactivity to a patients' cancer are expanded in vitro using a variety of means and then adoptively transferred into a cancer patient. T cells with a natural occurring reactivity to a patients cancer can be found in infiltrated in that patients' own tumors. The tumor is harvested, and these tumor infiltrating lymphocytes (TIL) are expanded in vitro using high concentrations of interluekin-2 (IL-2), anti-CD3 and allo-reactive feeders. These T cells are then transferred back into the patient along with exogenous administration of IL-2. Thus far, a 51% objective response rate has been observed; in some patients, tumors shrank to nondetectable size. In the case of engineered T cells, T cell receptors (TCR) that have been identified to have reactivity against tumor associated antigens are cloned into a replication incompetent virus that is capable of genomic integration. A patients own lymphocytes are exposed to these viruses and then expanded non-specifically or stimulated using the engineered TCR. The cells are then transferred back into the patient. This therapy has been demonstrated to result in objective clinical responses in patients with refractory stage IV cancer. The Surgery Branch of the National Cancer Institute (Bethesda, Maryland) is actively investigating this form of cancer treatment for patients suffereing aggressive melanomas.

Vaccination

Anti-microbial immunotherapy, which includes vaccination, involves activating the immune system to respond to an infectious agent.

Suppression

Immune suppression dampens an abnormal immune response in autoimmune diseases or reduces a normal immune response to prevent rejection of transplanted organs or cells.

Immune tolerance

Immune tolerance is the process by which the body naturally does not launch an immune system attack on its own tissues. Immune tolerance therapies seeks to reset the immune system so that the body stops mistakenly attacking its own organs or cells in autoimmune disease or accepts foreign tissue in organ transplantation. A brief treatment should then reduce or eliminate the need for life-long immunosuppression and the chances of attendant side effects, in the case of transplantation, or preserve the body's own function, at least in part, in cases of type 1 diabetes or other autoimmune disorders.

Allergies

Main article: Allergy immunotherapy

Immunotherapy is also used to treat allergies. While other allergy treatments (such as antihistamines or corticosteroids) treat only the symptoms of allergic disease, immunotherapy is the only available treatment that can modify the natural course of the allergic disease, by reducing sensitivity to allergens.

A three-to-five-year individually tailored regimen of injections may result in long-term benefits. Recent research suggests that patients who complete immunotherapy may continue to see benefits for years to come. Immunotherapy does not work for everyone and is only partly effective in some people, but it offers allergy sufferers the chance to eventually reduce or stop symptomatic/rescue medication.

The therapy is indicated for people who are extremely allergic or who cannot avoid specific allergens. For example, they may not be able to live a normal life and completely avoid pollen, dust mites, mould spores, pet dander, insect venom, and certain other common triggers of allergic reactions. Immunotherapy is generally not indicated for food or medicinal allergies. Immunotherapy is typically individually tailored and administered by an allergist (allergologist). Injection schedules are available in some healthcare systems and can be prescribed by family physicians. This therapy is particularly useful for people with allergic rhinitis or asthma.

The therapy is particularly likely to be successful if it begins early in life or soon after the allergy develops for the first time. Immunotherapy involves a series of injections (shots) given regularly for several years by a specialist in a hospital clinic. In the past, this was called a serum, but this is an incorrect name. Most allergists now call this mixture an allergy extract. The first shots contain very tiny amounts of the allergen or antigen to which you are allergic. With progressively increasing dosages over time, your body will adjust to the allergen and become less sensitive to it. This process is called desensitization. A recently approved sublingual tablet (Grazax), containing a grass pollen extract, is similarly effective, with few side effects, and can be self-administered at home, including by those patients who also suffer from allergic asthma, a condition which precludes the use of injection-based desensitisation. To read more about this topic, see: allergy and hyposensitization.

See also

• American Cancer Society