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Activation or suppression of the immune system to treat disease
The diagram above represents the process of chimeric antigen receptor T-cell therapy (CAR), this is a method of immunotherapy, which is a growing practice in the treatment of cancer. The final result should be a production of equipped T-cells that can recognize and fight the infected cancer cells in the body.
T-cells (represented by objects labeled as 't') are removed from the patient's blood.
Then in a lab setting the gene that encodes for the specific antigen receptors are incorporated into the T-cells.
Thus producing the CAR receptors (labeled as c) on the surface of the cells.
The newly modified T-cells are then further harvested and grown in the lab.
After a certain time period, the engineered T-cells are infused back into the patient.
Immunotherapy or biological therapy is the treatment of disease by activating or suppressing the immune system. Immunotherapies designed to elicit or amplify an immune response are classified as activation immunotherapies, while immunotherapies that reduce or suppress are classified as suppression immunotherapies.
Cancer treatment used to be focused on killing or removing cancer cells and tumors, with chemotherapy or surgery or radiation. These treatments can be very effective and in many cases are still used. In 2018 the Nobel Prize in Physiology or Medicine was awarded to James P. Allison and Tasuku Honjo "for their discovery of cancer therapy by inhibition of negative immune regulation." Cancer immunotherapy attempts to stimulate the immune system to destroy tumors. A variety of strategies are in use or are undergoing research and testing. Randomized controlled studies in different cancers resulting in significant increase in survival and disease free period have been reported and its efficacy is enhanced by 20-30% when cell-based immunotherapy is combined with conventional treatment methods.
One of the oldest forms of cancer immunotherapy is the use of BCG vaccine, which was originally to vaccinate against tuberculosis and later was found to be useful in the treatment of bladder cancer. BCG immunotherapy induces both local and systemic immune responses. The mechanisms by which BCG immunotherapy mediates tumour immunity have been widely studied, but they are still not completely understood.
The use of monoclonal antibodies in cancer therapy was first introduced in 1997 with rituximab, an anti-CD20 antibody for treatment of B cell lymphoma. Since then several monoclonal antibodies have been approved for treatment of various hematological malignancies as well as for solid tumors.
The current approaches for DC-based vaccination are mainly based on antigen loading on in vitro-generated DCs from monocytes or CD34+ cells, activating them with different TLR ligands, cytokine combinations, and injecting them back to the patients. The in vivo targeting approaches comprise administering specific cytokines (e.g., Flt3L, GM-CSF) and targeting the DCs with antibodies to C-type lectin receptors or agonistic antibodies (e.g., anti-CD40) that are conjugated with antigen of interest. Future approach may target DC subsets based on their specifically expressed C-type lectin receptors or chemokine receptors. Another potential approach is the generation of genetically engineered DCs from induced pluripotent stem cells and use of neoantigen-loaded DCs for inducing better clinical outcome.
Alternatively, Genetically engineered T cells are created by harvesting T cells and then infecting the T cells with a retrovirus that contains a copy of a T cell receptor (TCR) gene that is specialised to recognise tumour antigens. The virus integrates the receptor into the T cells' genome. The cells are expanded non-specifically and/or stimulated. The cells are then reinfused and produce an immune response against the tumour cells. The technique has been tested on refractory stage IV metastatic melanomas and advanced skin cancer.
Whether T cells are genetically engineered or not, before reinfusion, lymphodepletion of the recipient is required to eliminate regulatory T cells as well as unmodified, endogenous lymphocytes that compete with the transferred cells for homeostatic cytokines. Lymphodepletion may be achieved by myeloablative chemotherapy, to which total body irradiation may be added for greater effect. Transferred cells multiplied in vivo and persisted in peripheral blood in many people, sometimes representing levels of 75% of all CD8+ T cells at 6-12 months after infusion. As of 2012[update], clinical trials for metastatic melanoma were ongoing at multiple sites. Clinical responses to adoptive transfer of T cells were observed in patients with metastatic melanoma resistant to multiple immunotherapies.
Anti-PD-1/PD-L1 and anti-CTLA-4 antibodies are the two types of checkpoint inhibitors currently available to patients. The approval of anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and anti-programmed cell death protein 1 (PD-1) antibodies for human use has already resulted in significant improvements in disease outcomes for various cancers.
Although these molecules were originally discovered as molecules playing a role in T cell activation or apoptosis, subsequent preclinical research showed their important role in the maintenance of peripheral immune tolerance.
These therapies have revolutionized cancer immunotherapy as they showed for the first time in many years of research in metastatic melanoma, which is considered one of the most immunogenic human cancers, an improvement in overall survival, with an increasing group of patients benefitting long-term from these treatments.
Immunosuppressive drugs help manage organ transplantation and autoimmune disease. Immune responses depend on lymphocyte proliferation. Cytostatic drugs are immunosuppressive. Glucocorticoids are somewhat more specific inhibitors of lymphocyte activation, whereas inhibitors of immunophilins more specifically target T lymphocyte activation. Immunosuppressive antibodies target steps in the immune response. Other drugs modulate immune responses and can be used to induce immune regulation. It has been observed in a preclinical trial that regulation of the immune system by small immunosuppressive molecules such as Vitamin D and Dexamethasone, administered under a low-dose regimen and subcutaneously, could be helpful in preventing or treating chronic inflammation.
The body naturally does not launch an immune system attack on its own tissues. Models generally identify CD4+ T-cells at the centre of the autoimmune response. Loss of T-cell tolerance then unleashes B-cells and other immune effector cells on to the target tissue. The ideal tolerogenic therapy would target the specific T-cell clones co-ordinating the autoimmune attack.
Immunotherapy may produce long-term benefits. Immunotherapy is partly effective in some people and ineffective in others, but it offers allergy sufferers a chance to reduce or stop their symptoms.
The therapy is indicated for people who are extremely allergic or who cannot avoid specific allergens.
IgE-mediated food allergy is a global health problem that affects millions of persons and affects every aspect of life for the patient. A promising approach to treat food allergies is the use of oral immunotherapy (OIT). OIT consists in a gradual exposure to increasing amounts of allergen can lead to the majority of subjects tolerating doses of food sufficient to prevent reaction on accidental exposure. Dosages increase over time, as the person becomes desensitized. This technique has been tested on infants to prevent peanut allergies.
Allergen-specific immunotherapy (ASIT) has become the gold standard for the causative treatment for IgE-mediated allergic diseases for a large variety of allergens. One may curiously await the new developments, which will further enhance our understanding of allergy mechanisms and improve ASIT for the next generations of patients and physicians.
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