Mechanisms of the Bystander Effect
Generations of students in radiation biology have been taught that heritable biological damage requires direct damage to DNA. We now know that this is not true. The Bystander Effect is the name given to the phenomenon whereby biological effects are observed in cells that are not themselves traversed by a charged particle, but are in close proximity to cells that are. Several research groups have convincingly demonstrated a bystander effect for alpha particle, which are heavy and high LET, because charged particles can be focused into a tiny beam that can be directed onto individual cells. The biological effects seen in adjacent non-hit cells clearly represents a bystander effect. It is not so easy to demonstrate a similar effect for x-rays or for the electrons set in motion by the absorption of x-rays. In this project we used two types of cell that could be recognized one from the other. One cell type was fed radioactive tritiated thymidine, which is incorporated into the DNA, . The tritium emits electrons which have a very short range so that they do not even get out of the cell. These cells were then mixed with a different type of cell which are routinely used to assess mutations. The mixed cells formed a cluster, where the two types of cells were in close contact, and left for some hours. Subsequently, the two types of cells were separated and studied. A substantial fraction of the cells that had incorporated the tritiated thymidine were killed by the radiation. The interesting finding is that the cells that had not incorporated tritiated thymidine, but had been in close contact with cells that had, exhibited a significant incidence of mutations. These experiments clearly demonstrated a bystander effect for low LET electrons. In further experiments, it was possible to show that the bystander effect was greatest when the two cell types were in gap junction communication.
- Research Organization:
- Center for Radiological Research, Columbia University Medical Center, New York, NY
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- FG02-03ER63441
- OSTI ID:
- 934812
- Report Number(s):
- DOE/ER/63441; TRN: US1001083
- Country of Publication:
- United States
- Language:
- English
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