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Activating the Immune Response
These types of therapies activate the immune system to provide protection from disease, or to induce the immune system to mount a response to something to which it would not normally respond.
The oldest and most well-known example of immunotherapy is vaccination, in which the immune system is primed to respond to a pathogen which it has not yet encountered. This type of immunotherapy is used to prevent infection with diseases which are potentially fatal or severely harmful, such as smallpox (which, thanks to a rigorous world-wide vaccination program, has been entirely eradicated), rubella, and polio.
- Cancer “Vaccines”
This type of immunotherapy attempts to activate an immune response against antigens expressed on the surface of tumor cells. When cells become cancerous, they often begin producing proteins which are not produced by normal cells – so activating an immune response against these proteins can be done safely without damaging healthy cells and tissues. Therapies generally involve removing T cells from a patient, and priming them in vitro to respond to antigens taken from the patient’s tumor. The cells are then injected back into the patient, often with a dose of interleukin-2, a cytokine which promotes T cell growth.
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Suppressing the Immune Response
Some types of immunotherapy are carried out to suppress the immune response, typically to treat allergies or autoimmune disorders, or to prevent transplant rejection.
- Allergic and Autoimmune Responses
Many treatments for allergies simply suppress the effects – immunotherapy, which modulates the immune response to prevent allergic reactions from occurring, is the only therapy which can actually reduce an individual’s sensitivity to allergens. This type of therapy involves injections of minute doses of allergen. The dosage increases gradually over time, and with successful treatment eventually results in tolerance to what was once an allergen.
In the case of autoimmune disorders, immunotherapy typically involves suppression of the adaptive immune response in a much more general way, and often leads to increased susceptibility to certain types of infection for people who receive this treatment.
- Preventing Transplant Rejection
As with autoimmune treatments, preventing transplant rejection can involve suppressing the entire adaptive immune system, leading to increased infection susceptibility.
New strategies for preventing transplant rejection and autoimmune disorders involve attempting to make the immune system tolerant to the antigens which are causing the unwanted immune reaction.