Bystander effect (radiobiology)
Encyclopedia
The Radiation-Induced Bystander Effect (Bystander Effect) is the phenomenon in which unirradiated cells exhibit irradiated effects as a result of signals received from nearby irradiated cells.
There is evidence that targeted cytoplasmic irradiation results in mutation
in the nucleus
of the hit cells. Cells that that are not directly hit by an alpha particle
, but are in the vicinity of one that is hit, also contribute to the genotoxic response of the cell population.
Similarly, when cells are irradiated, and the medium is transferred to unirradiated cells, these unirradiated cells show bystander responses when assayed for clonogenic survival and oncogenic transformation. This is also attributed to the bystander effect.
The demonstration of a bystander effect in 3D human tissues and, more recently, in whole organisms have clear implication of the potential relevance of the non-targeted response to human health.
This effect may also contribute to the final biological consequences of exposure to low doses of radiation.
Note that the Bystander Effect is NOT the same as the Abscopal Effect. The Abscopal Effect is a phenomenon where the response to radiation is seen in an organ/site distant to the irradiated organ/area, that is, the responding cells are not juxtaposed with the irradiated cells. T-cells and dendritic cells have been implicated to be part of the mechanism.
There is evidence that targeted cytoplasmic irradiation results in mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
in the nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
of the hit cells. Cells that that are not directly hit by an alpha particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
, but are in the vicinity of one that is hit, also contribute to the genotoxic response of the cell population.
Similarly, when cells are irradiated, and the medium is transferred to unirradiated cells, these unirradiated cells show bystander responses when assayed for clonogenic survival and oncogenic transformation. This is also attributed to the bystander effect.
The demonstration of a bystander effect in 3D human tissues and, more recently, in whole organisms have clear implication of the potential relevance of the non-targeted response to human health.
This effect may also contribute to the final biological consequences of exposure to low doses of radiation.
Note that the Bystander Effect is NOT the same as the Abscopal Effect. The Abscopal Effect is a phenomenon where the response to radiation is seen in an organ/site distant to the irradiated organ/area, that is, the responding cells are not juxtaposed with the irradiated cells. T-cells and dendritic cells have been implicated to be part of the mechanism.