immunotherapy

immunotherapy, medical treatment in which the body’s own cells or chemicals are used to help the natural immune response work against disease. Immunotherapy is mainly used in the treatment of cancer, though it is also sometimes used to treat autoimmune diseases.

Immunotherapy leverages the ability of the immune system to detect and attack antigens (foreign substances). In the case of cancer, for example, certain types of immunotherapy are designed to target so-called tumor-specific antigens, which are found only on the surface of cancer cells. These antigens are altered forms of normal self-antigens and are therefore foreign. They effectively evade recognition by the immune system through various mechanisms, such as by blocking immune activity, interfering with antigen recognition, or exhausting immune cells known as T cells, causing the T cells to lose their ability to attack and destroy cancer cells. Some immunotherapeutic strategies are oriented toward removing the inhibitory actions of disease-associated proteins, whereas others attempt to directly increase immune activity.

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cancer: Immunotherapy

Types of immunotherapy

There are different forms of immunotherapy, including adoptive cell transfer, monoclonal antibodies, immune checkpoint inhibitors, and therapeutic vaccines. Adoptive cell transfer is carried out in different ways, though a common and often effective approach is CAR T-cell therapy. This type of treatment involves collecting both immune and cancer cells from a patient and then testing the immune cells to determine which ones are most active against the cancer cells. Those that are most active are then modified to possess a chimeric antigen receptor (CAR), which further augments their ability to attack the cancer cells. The modified cells are then grown in large populations and transferred back into the patient’s body. This form of immunotherapy is most commonly used to treat leukemia in children and lymphoma in adults.

Monoclonal antibodies are produced artificially through genetic engineering and related techniques. In this case circulating B cells (a type of immune cell) become activated by the presence of an antigen and multiply to form a clone of plasma cells, each secreting identical antibodies. When derived from the descendants of a single B cell, such antibodies are referred to as monoclonal antibodies. Monoclonal antibodies have been used in the treatment of various autoimmune disorders, including lupus erythematosus and rheumatoid arthritis, as well as some types of cancer.

Immune checkpoint inhibitors are drugs that work by blocking immune checkpoints, which are proteins that regulate immune responses to prevent overblown immune activity. Thus, immune checkpoint inhibitors, by blocking the activity of checkpoint proteins, enable immune cells to mount a more powerful response to cancer cells than they would otherwise. Examples of checkpoint proteins include cytotoxic T-lymphocyte associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and programmed death-ligand 1 (PD-L1). Immune checkpoint inhibitors targeting these proteins are known generally as anti-CTLA-4, anti-PD-1, and anti-PD-L1, respectively; such agents have been effective in the treatment of certain cancers, including head and neck squamous cell cancer, Hodgkin lymphoma, melanoma, non-small cell lung cancer, and renal cell carcinoma.

Vaccines that stimulate an immune response against antigens are potentially strong enough to eliminate cancer or other diseases. In general such vaccines differ from those used to prevent disease. In cancer treatment, for example, vaccines may be developed in a way that is similar to CAR T-cell therapy, wherein the vaccine is made from the patient’s own tumor cells. In other instances vaccines are made using a patient’s own dendritic cells (a kind of immune cell), which are then tailored to stimulate the immune system to respond to a tumor-specific antigen on the patient’s cancer cells; an example of a dendritic cell vaccine is sipuleucel-T, an agent used to treat prostate cancer. Vaccines can also be made to target antigens that occur on cells of a specific cancer type that affects many people, thereby making the vaccines less individualized but potentially more cost-effective and more broadly applicable.

Side effects

Immunotherapy is associated with various side effects, the most serious among them being severe allergic reactions, which are rare. More typically, patients experience side effects ranging from pain and swelling at the injection site to flulike symptoms, including chills, fever, and headache, which can be indicative of an immune response. Heart palpitations, organ inflammation, and weight gain from fluid retention can also occur.