Immune aging increases a person’s risk of developing diseases such as cancer and cardiovascular disease, as well as increased susceptibility to infection. Researchers from the University of Southern California (USC) have showed that stress plays a crucial part in aging of the immune system in same-age adults, and propose a little-known therapeutic intervention.

With aging comes a natural decline in the immune system, a condition called immunosenescence. Immunosenescence includes too many worn-out white blood cells circulating and too few fresh, “naive” white blood cells (T cells) ready to take on new invaders.

[T-cells are a critical component of immunity: T cells mature in a gland called the thymus, which sits just in front of and above the heart. As people age, the tissue in their thymus shrinks and is replaced by fatty tissue, resulting in reduced production of immune cells. This process is accelerated by lifestyle factors like poor diet and low exercise, which are both associated with stress.]

Immune aging is associated not only with disease, but also hastens organ system aging and reduces the receptivity and efficacy of vaccines.

USC researchers sought to find how much of immune aging was influenced by social stress: they queried and cross-referenced enormous data sets from a national longitudinal study of economic, health, marital, family status, and public and private support systems of older Americans (University of Michigan’s Health and Retirement Study).

In addition, USC researchers analysed questionnaire responses from a national sample of 5,744 adults over the age of 50. The questionnaire was designed to assess respondents’ experiences with stressful life events, chronic stress, everyday discrimination, and lifetime discrimination. Flow cytometry was used to analyse the participants’ blood samples to gauge immune activity.

As expected, people with higher stress scores had “older” immune profiles, with lower percentages of fresh disease fighters and higher percentages of worn-out white blood cells. The association between stressful life events and fewer T cells remained strong even after controlling for education, smoking, drinking, weight (BMI), and race or ethnicity.

“In this study, after statistically controlling for poor diet and low exercise, the connection between stress and accelerated immune aging wasn’t as strong,” said Eric Klopack, a postdoctoral scholar in the USC Leonard Davis School of Gerontology. “What this means is people who experience more stress tend to have poorer diet and exercise habits, partly explaining why they have more accelerated immune aging.”

Improving diet and exercise behaviours in older adults may help offset the immune aging associated with stress.

USC researchers also highlight a common virus that is known to have a strong effect on accelerating immune aging. Cytomegalovirus (CMV) is an asymptomatic virus in humans. CMV is dormant most of the time but can flare up, especially when a person is experiencing high stress – CMV vaccination could be a simple and potentially powerful intervention that could reduce the immune aging effects of stress.

A new study from the University of Birmingham has uncovered how patients on heavy antibiotics use are at risk of fungal infection because of disruptions to their immune system. The study involved patients at a UK hospital – patients treated with antibiotics to prevent bacterial infections and sepsis instead developed fungal infections particularly caused by the candida fungus.

Candida infections are generally superficial but in some cases the fungus can enter the bloodstream causing what is known as invasive candidiasis which can be fatal.

A team in the University’s Institute of Immunology and Immunotherapy, in conjunction with US researchers at the National Institutes of Health, discovered that antibiotics disrupted the immune system in the intestines, meaning that fungal infections were poorly controlled in that area. Unexpectedly, the team also found that where fungal infections developed, gut bacteria were able to escape, leading to the additional risk of bacterial infection.

Through animal experiments and analysis of hospital records, the researchers showed that co-infections were likely to occur in humans after they have been treated with antibiotics.

“We knew that antibiotics make fungal infections worse, but the discovery that bacterial co-infections can also develop through these interactions in the gut was surprising,” said Birmingham fellow, Dr. Rebecca Drummond. “These factors can add up to a complicated clinical situation – and by understanding these underlying causes, doctors will be better able to treat these patients effectively.”

The researchers later revealed that treatment with immune-boosting drugs might help counteract the harm of antibiotics in patients in dire need of it.

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New research that examined data from ToxCast, the Environmental Protection Agency’s toxicity screening database, is raising questions over the safety of a commonly used food preservative known as tert-butylhydroquinone (tBHQ) or E319. The compound is suspected to disrupt immune functions, although both the United States and European health authorities deem the additive safe in low concentrations.

Public health researchers are calling for greater surveillance of the immunological effects of food additives, especially those that may harm the immune system’s defense against infection or cancer, as with tBHQ.

According to Scott Faber, from the Environmental Working Group – a non-profit organisation sponsoring the new research – the United States Food and Drug Administration (FDA) does not re-evaluate previously approved food additives when new science becomes available, while food manufacturers have no incentive to change their formulas.

“Too often, the FDA allows the food and chemical industry to determine which ingredients are safe for consumption. Our research shows how important it is that the FDA take a second look at these ingredients and test all food chemicals for safety.”

The study suggested the ToxCast data, which is based on animal* and mechanistic studies, reveals a number of signs tBHQ influences immune activity. Further investigation needs to be done to better understand how this compound affects human immune parameters, including “defense against infection, anti-tumour immune responses, and autoimmune reactivity.”

[*An animal study published in 2019 found mice raised on a diet with tBHQ displayed impaired immune responses to influenza infections.]

“From the public policy perspective, the discovery of impacts on human health of substances that have long been used in consumer products and food products suggests that the pre-market safety evaluation of these substances was inadequate,” the researchers concluded. “We recommend that immunotoxicity testing should be prioritised in order to protect public health, and immunotoxicity analysis should be, in our estimate, an integral part of chemical safety assessment.”

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