Pollution affects the immune system

Maternal exposure to a ubiquitous form of industrial pollution is capable of damaging an offspring’s immune system, according to a new study. This damage is even passed onto future generations, undermining the body’s ability to defend itself against infections. Dr. B Paige Lawrence led the research in collaboration with the University of Rochester Medical Center’s Department of Environmental Medicine. The study was published in Cell Press’ journal iScience. Experimentation was performed on mice, since their immune system function is not particularly different from that of humans.

“The old adage ‘you are what you eat’ is a touchstone for many aspects of human health. But in terms of the body's ability to fight off infections, this study suggests that, to a certain extent, you may also be what your great-grandmother ate,” explained Lawrence, in a University of Rochester Medical Center press release.

Since the pollution weakens the immune system over multiple generations, it might serve as an explanation for the many variations seen during flu episodes. The protective effect of the flu vaccine varies among different individuals. In the midst of pandemic flu outbreaks, some are not heavily affected by the flu, whereas others might become very sick. Age, mutations of the virus, and many other factors provide an explanation for some of these variations. However, the diversity of immune responses to flu infection is not fully accounted for by these factors.

“When you are infected or receive a flu vaccine, the immune system ramps up production of specific kinds of white blood cells in response,” Lawrence said. “The larger the response, the larger the army of white blood cells, enhancing the ability of the body to successfully fight off an infection. Having a smaller size army — which we see across multiple generations of mice in this study — means that you're at risk for not fighting the infection as effectively.”

The researchers conducted their experiment by exposing pregnant mice to a chemical known as dioxin in levels similar to that of the environment. Dioxin is a typical byproduct of industrial production as well as the incineration of waste. Some consumer products have this chemical as well. In any of these cases, dioxin eventually infiltrates food products and is eaten by humans. Dioxins bioaccumulate, and are thus found rather frequently in animal-based food.

Cytotoxic T cells are white blood cells that protect the body from foreign pathogens that include bacteria and viruses. They find and eliminate cells with mutations that may cause cancer. These blood cells were produced less frequently and exhibited impaired function when the mice in the study were infected with the influenza A virus. The researchers saw this effect in the offspring of female mice exposed to dioxin, as well as in subsequent generations; the effect even impacted their “great-grandchildren,” so to speak. Female mice, the study found, were affected more than male mice.

The hypothesis of the researchers was based on the fact that dioxin binds to a protein known as AHR which is found in cells. They believe that dioxin alters genetic instructions’ transcription in some way, that dioxin changes the cellular machinery which causes genes to be expressed, and that future generations inherit this alteration.

All in all, the research provides another frightening insight into how anthropogenic emissions, especially of harsh chemicals such as dioxin, can harm the human quality of life for generations to come.