Radiation appears to have a modulating effect on the immune system, which can result in increased susceptibility to infections. The specific effects of radiation on the immune system can depend on the type of radiation and the dose. There is a significant difference, for example, between therapeutic radiation for breast cancer and exposure to an atom bomb. In cases where exposure is high enough to cause concern, a doctor may recommend an evaluation and discuss treatment options.
Patients exposed to high doses of radiation may experience widespread cell death throughout their bodies, including the death of immune cells. Smaller doses, like those used in cancer therapy, have localized effects. The immediate effects of radiation on the immune system can include damage to the helper T cells and other lymphocytes that control immune responses. In addition, natural killer cells may be destroyed, along with bone marrow. Very high levels of radiation exposure can increase the chance that the patient will die of an infection before the immune system has an opportunity to recover.
Long term effects of radiation on the immune system may include a decreased ability to produce new T cells in people exposed to high amounts of ionizing radiation. This can include victims of nuclear bombs or people exposed to dangerous radiation in accidents. The inability to make new T cells can mean that they are less able to respond to new infectious organisms. Their immune memory will protect them from antigens they were exposed to in the past, but new immunities may have difficulty forming.
Carefully controlled doses of radiation like those used in nuclear medicine are calibrated to minimize damage. The effects of radiation on the immune system in this context can include a period of immunodepression after radiation treatments, sometimes compounded by the use of certain medications. This is considered an acceptable tradeoff, given the clear benefits of destroying or controlling cancerous cells. Procedures like nuclear imaging studies are also reasonably safe, and the benefits of the testing may outweigh the risks of the radiation exposure.
Exposure to dangerous levels of ionizing radiation can cause immediate as well as long term health concerns, including worries about the effect of radiation on the immune system. The patient may need monitoring, including regular blood tests to check on immune function. Studies also suggest that ultraviolet exposure can potentially have an immunosuppressive effect if it occurs in high volumes. Patients can protect themselves from excessive sun exposure with clothing, sunblock, and changes in habit to avoid the most intense sun of the day.