Bystander-Cells Affected by Radiation

Source: Proc Natl Acad Sci U S A. 2005 October 4; 102(40): 14203–14208.
http://www.pubmedcentral.gov/articlerender.fcgi?artid=1202386

Applied Biological Sciences

A central tenet in understanding the biological effects of ionizing radiation has been that the initially affected cells were directly damaged by the radiation.

By contrast, evidence has emerged concerning “bystander” responses involving damage to nearby cells that were not themselves directly traversed by the radiation.

These long-range effects are of interest for assessing risks from low-dose exposures, where only a small proportion of cells are directly hit.

Unirradiated cells up to 1 mm distant from irradiated cells showed a significant enhancement in effect over background, with an average increase in effect of 1.7-fold for micronuclei and 2.8-fold for apoptosis.

The surprisingly long range of bystander signals in human tissue suggests that bystander responses may be important in extrapolating radiation risk estimates from epidemiologically accessible doses down to very low doses where non-hit bystander cells will predominate.