The immune system: why some people get sick more often

About the group Sunil Ahuja from Health Sciences Centre from the University of Texas In the journal Nature Communications. A variety of human and animal studies combined to develop their concept of immune plasticity. With just two parameters, I was able to explain the health history of nearly 50,000 people.

Ahuja tells science that the uneven course of infection, among others with HIV/AIDS, has long puzzled medicine. 30 percent of children. The same applies to people with hemophilia: unfortunately, many initially received HIV-contaminated products, but the majority did not become infected. And even after contracting HIV, the disease progressed in a completely different way: some were doing very well, while others died very quickly without treatment. With Covid-19 it’s the same.”

Age is not enough to explain

Statistically, getting older means an increased risk of severe Covid cycles, but there are also many cases of elderly people surviving the disease very well, while younger people died without identifiable risk factors.

These atypical cycles cannot be explained by age or genetics alone, says the professor of medicine, microbiology, immunology and biochemistry, who researches mainly HIV/AIDS, allergies, autoimmune diseases and aging phenomena. In the end, the team came up with a combination of two factors.

Factor 1: CD4/CD8 ratio

The first of the two scales is not new. To date, it has been used, among other things, to measure how the immune system develops over time in people with HIV. It is the ratio of two types of immune cells: CD4+ T-type helper cells (T lymphocytes) and CD8+ cytotoxic T cells (formerly killer T cells). According to Ahuja’s group, a certain minimum number of CD4+ cells and a relative increase in CD8+ cells in comparison results in an optimal immune status.

Factor 2: patterns of gene activity

In the COVID-19 pandemic, certain patterns of activity have been identified for the genes and proteins that produce them: some are prevalent in people who recover quickly or who don’t get sick at all; Others are found in large numbers in those who have had severe cycles and some have died. According to Ahuja, those who have a lot of the first and a little of the second can deal better with infections and infections and also have a higher chance of living a long life.

Immunoplasticity measure

As a result, the team developed four levels of immune health: immune health scores IHG-I through -IV. According to Ahuja, these values ​​are universal. It can be measured in all humans, in non-human primates as well as in mice. The average immune health is poorer in chronically exposed populations; For example in developing countries, where vermiform schistosomiasis is common. Ahuja says this is why HIV can do more damage in parts of Africa than in Europe.

The constitution can change

If you get sick, says Ahuja, it initially means that your immune resilience has decreased. However, people who previously had good stats tend to recover their immunity quickly. However, some recover from symptoms, for example after the flu, but the levels of immune resilience do not return to previous levels. When you check them out six months later, some people still have a slight disability. If these people become infected the second time, they will be more likely to develop a more severe infection.”

Exercising and getting enough sleep

Ajuha’s team recommends monitoring immune resilience. At her institute, this is already being done for patients at risk and in suspected cases. According to Ahuja, the scan costs about $100. If the immune resistance is low, you can search for the cause and take countermeasures.

Ahuja has not yet conducted a systematic study on what measures can raise the immune health score. However, some of the data sets examined show that daily exercise in particular has a positive effect on the values. Immune cells have already been shown to benefit from adequate sleep, most recently in a study he conducted Icahn School of Medicine at Mount Sinai in New York City. One study that Ahuja analyzed also showed that positive genetic signatures became more pronounced during REM sleep.

Infection – risk or opportunity?

“I don’t know if I would be resilient if I never attacked,” Ahuja says in an interview with Science.ORF.at. Whether an infection is beneficial or detrimental to immune health in the long run depends on how appropriately the immune system responds to it: “It needs the right amount, in the right place, at the right time, and of the right kind.”

Why do women live longer

Incidentally, health-promoting gene imprints are increasingly being found in women and are also linked to longevity. Therefore, the concept of immune resilience could also explain why women live statistically longer than men, says Ahuja. It is suspected that there is an evolutionary biological reason behind this: good immune resistance in women during pregnancy promotes the health of the fetus and thus the preservation of the species. Ahuja says the current findings make it unlikely that the hormonal difference between the sexes is solely responsible for a woman’s longevity. Because better immunity levels last until menopause.

The group does not exclude that other factors may influence the course of immune resilience over the lifespan. Among other things, the involution of the thymus gland and the decrease in the production of stem cells are called into question for them.