Engineered T-cell

Chimeric antigen receptors (CARs, also known as chimeric immunoreceptors, chimeric T cell receptors or artificial T cell receptors) are engineered receptors that combine a new specificity with an immune cell to target cancer cells. Typically, these receptors graft the specificity of a monoclonal antibody onto a T cell. The receptors are called chimeric because they are fused of parts from different sources. CAR-T cell therapy refers to a treatment that uses such transformed cells for cancer therapy.

The basic principle of CAR-T cell design involves recombinant receptors that combine antigen-binding and T-cell activating functions. The general premise of CAR-T cells is to artificially generate T-cells targeted to markers found on cancer cells. Scientists can remove T-cells from a person, genetically alter them, and put them back into the patient for them to attack the cancer cells. Once the T cell has been engineered to become a CAR-T cell, it acts as a "living drug". CAR-T cells create a link between an extracellular ligand recognition domain to an intracellular signalling molecule which in turn activates T cells. The extracellular ligand recognition domain is usually a single-chain variable fragment (scFv). An important aspect of the safety of CAR-T cell therapy is how to ensure that only cancerous tumor cells are targeted, and not normal cells. The specificity of CAR-T cells is determined by the choice of molecule that is targeted.

CAR-Ts can be derived from either a patient's own blood (autologous) or derived from another healthy donor (allogenic). These T-cells are genetically engineered to express an artificial T cell receptor, through which they are targeted to disease-related antigens. This process is independent and thus the targeting efficiency is greatly increased. These CAR-T cells are programmed to target antigens that are present on the surface of tumors. When they come in contact with the antigens on the tumors, the CAR-T cells are activated via the signal peptide, proliferate and become cytotoxic. The CAR-T cells destroy the cancer cells through mechanisms such as extensive stimulated cell proliferation, increasing the degree to which the cell is toxic to other living cells i.e. cytotoxicity, and by causing the increased production of factors that are secreted from cells in the immune system that have an effect on other cells in the organism. These factors are called cytokines and include interleukins, interferons and growth factors.

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