Effect: What are CAR T-cells and how do they work?
Author: Julia Dobke, Editor: Maria Yiallouros, English Translation: Dr. med. Gesche Riabowol (geb. Tallen), Last modification: 2025/12/04 https://kinderkrebsinfo.de/doi/e217369
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Chimeric antigen receptor T cells (CAR T cells) are genetically engineered cells of a patient [see genetic engineering]. They are produced from the patient's T lymphocytes, i.e. they stem from the body's own (autologous) cells. CAR T cells are used to recognise malignant cancer cells that would normally not be attacked by the original T lymphocytes.
T lymphocytes: tasks in the immune system
The immune system consists of various components that collaborate to ensure an efficient immune response to a pathogen. An important group of immune cells are the T lymphocytes (also called T cells). T lymphocytes or T cells are formed in the bone marrow and go through a maturation phase in a specific, relatively small organ in the chest area, the thymus gland. In this phase, the T lymphocytes learn to recognise pathogens or altered (mutated) endogenous cells in an individual’s body so that the entire immune system can get ready for an attack. This property of the T cells is used for the production of CAR T cells.
The surface of T lymphocytes presents with many identical structures (so-called receptors). These receptors serve to recognise specific foreign proteins named antigens, which can be found, for example, on the cell surface of a pathogen or on a body cell that is infected with a virus. Once the T lymphocyte has identified a cell carrying a cer-tain antigen, the matching T cell receptor will bind to it and the cell is subsequently destroyed.
Effect and production of CAR T cells
The novel cell therapy with CAR T cells makes use of the principle of action of T lymphocytes described above: usually, leukaemia (or other malignant) cells are not directly recognised as harmful by the patient's own immune defences. The T lymphocytes must first be artificially enabled to recognise, for example, leukaemia cells as foreign in order to destroy them. Therefore, they are genetically modified in a special laboratory so that the receptors on their cell surface are capable of identifying the proteins (antigens) on the cell surface of leukaemia cells as harmful in order to subsequently destroy them.
For genetic modification, the T lymphocytes are filtered from the patient’s blood by a special procedure called leukapheresis. The T lymphocytes obtained in this way are sent to a special laboratory that has permission to produce CAR T cells. To do so, a new antigen receptor with special properties is inserted into the patient’s T lymphocytes using a virus for the transport (called viral vector). Since this antigen receptor consists of different building block-patterns that usually do not present this way, it is also called the chimeric antigen receptor (CAR).
For example, the artificial receptor can recognize the antigen CD19 of B lymphocytes (also B cells), which is found on the surface of many leukaemia cells in acute lymphoblastic leukaemia (as well as on certain lymphoma cells). As a result, CAR T cells are able to destroy these B leukaemia or B lymphoma cells.
Reinfusion of T lymphocytes as CAR T cells
The CAR T cells are reinfused into the patient by transfusion via a central venous catheter. The artificial antigen receptor of the T lymphocytes now recognises the patient’s leukaemia or lymphoma cells, which present the antigen CD19 on their surface, as harmful and destroys them.
The CAR T cells are also able to continue dividing in the patient's body and can remain active there for a longer period of time.