Ionizing radiations cause damage to every cell in the body. However, the cells of the immune system are especially vulnerable to radiation exposure.
Your immune system is a very complex and large network of cells, organs, hormones and other components that collaboratively work to protect the body from bacteria, virus and even cancer cells, thus keeping you safe from all kinds of infections and diseases.
How ionizing radiation weakens the immune system?
The immune system consists of different kinds of cells, each specialized to do its own job. These cells, responsible for body’s innate and adaptive immunity, initially originate from the bone marrow. The bone marrow produces white blood cells that further differentiate into monocytes, macrophages, neutrophils, granulocytes, dendritic cells, B cells, T cells and natural killer cells.
Now, the cells most affected by nuclear radiations are those that are rapidly multiplying. It is because a cell’s DNA is most exposed during this stage. Since cancer cells are rapidly dividing cells, this is how radiotherapy (radiation exposure) works to eliminate these cells. However, there are other healthy cells that are multiplying at a rapid pace too, for example cells in the bone marrow.
Bone marrow contains stem cells that rapidly and constantly divide to produce different types of blood cells – red blood cells, white blood cells and platelets. Some of these cells mature in the bone marrow itself and then migrate into the bloodstream, whereas other cells (precursors to mature cells) migrate to other tissues to complete their maturation. For example, white blood cells mature into T cells in the thymus gland.
Since there is a lot of cell division taking place in the bone marrow, bone marrow is particularly sensitive to drugs, radiation and toxic chemicals. Radiation exposure kills immature bone marrow stem cells as well as other cells that are in various stages of maturation in the blood marrow.
Many of the symptoms of acute radiation sickness are primarily because of the damage inflicted to the bone marrow cells. For example, high doses of radiation cause bleeding from the nose, mouth, gums, and rectum as radiation destroys platelets, cells that helps blood to clot. It also causes an increased risk of bacterial, viral, and fungal infections due to the suppression of disease fighting white blood cells. Similarly, decreased numbers of red blood cells cause weakness and anemia.
What about chronic, low dose radiation exposure? Well, research tells us that there is no safe threshold. Even low dose radiations can cause damage to the immune system and trigger DNA mutations in the marrow, causing leukaemia or blood cancer. Persistent exposure to low dose radiation wreaks havoc through excessive generation of free radicals. These highly reactive, highly unstable molecules cause damage to DNA, lipids and proteins.
Lymphocytes, particularly T cells, are highly sensitive to radiation damage. A 2015 study found that ionizing radiation impairs activation of T cells. T cells are ferocious immune cells that hunt down and kill infected cells or cells that have turned cancerous. These cells usually remain in a dormant state unless stimulated by an antigen (a foreign substance that triggers the immune system to produce anti-bodies). The receptors on T cells engage with the antigen and signal the sleeping T cells to wake up and multiply. During this activation process, T cells undergo metabolic changes to meet higher energy demands of cell growth, failing which they are not able to complete their transition from resting to activated stage. The study showed that ionizing radiation disrupts metabolic transformation during T cell activation. 
A recent 2017 study found that “low-dose radiation effects are partially due to the hematopoietic stem cell impairment” and the findings show that “acute low-dose radiation exposure specifically results in long-term alterations of the T-lymphocyte repertoire.” 
After any nuclear fall-out, such as in Chernobyl or Japan’s Fukushima nuclear accident, radiation exposure also comes through consuming contaminated food. With their capacity to mimic real nutrients (for example, Cs 137 mimics potassium, Strontium-90 as calcium, Iodine 131 as iodine and Plutonium-239 as iron), these radioactive isotopes easily enter the body and become deposited in various tissues, causing long-term free radical damage to all cells including those of the immune system.
As reported by The Nuclear Reader, “The everyday releases of low-level radioactivity by nuclear power plants has been found to cause several kinds of health damage; including premature births, congenital defects, infant mortality, mental retardation, heart ailments, arthritis, diabetes, allergies, asthma, cancer, genetic damage and chronic fatigue syndrome. It has been linked to previously unknown infectious diseases and the resurgence of old ones by damaging the developing white blood cells originating in the bone marrow and thus weakening the immune system.” 
In addition, low dose radiation is believed to cause mutations in bacteria and viruses. Scientists believe this may be why we are seeing a rise in new diseases such as Reye’s Syndrome, Legionnaires’ disease and Lyme disease.
In a nutshell, radiation causes severe damage to bone marrow stem cells, where immune cells originate. Any damage to these fighter cells supresses overall immunity and make people susceptible to opportunistic infections, cancer and other disease.
You can give your body the tools to up its immune defense and the capacity to neutralize the free radicals. Foods and supplements rich in anti-oxidants and cancer fighting substances can go a long way in helping the body to protect itself from the harmful effects of radiation exposure.
- Heng-Hong Li et al. Ionizing Radiation Impairs T Cell Activation by Affecting Metabolic Reprogramming. Int J Biol Sci. 2015
- SM Candéias et al. Low-dose radiation accelerates aging of the T-cell receptor repertoire in CBA/Ca mice. Cell Mol Life Sci. 2017
- CHAPTER ONE: HAZARDS OF LOW LEVEL RADIOACTIVITY. NuclearReader.info