An electron microscope image of the SARS-CoV-2 virus/NIAID

If you are among the minority of Americans yet to catch the pandemic disease Covid-19, or one of the majority who suffered a very mild case, thank your T cells.

The all-around, utility players in the natural human response to disease, T cells were early on identified as a major player in determining who would come down with Covid-19 after exposure to the then-new and novel SARS-CoV-2 discovered in China in late 2019.

Now, a team of researchers from the University of Pennsylvania and the Children’s Hospital of Philadelphia have identified in these cells a natural ability to fight disease that dates back who knows how far in our evolutionary history.

“These data highlight the complexity of precursor T cell repertoire and implicate non-infectious exposures to common microbes as a key factor that shapes human pre-existing immunity to SARS-CoV-2,” they reported in a peer-reviewed study published in Science Immunology late last week.

They concluded the study with a strong pitch for paying more attention to the importance of these cells.

“These findings highlight the breadth of T cell recognition and suggest that life-long exposures to a diverse microbial environment could have profound impacts on the composition of the immune repertoire,” they wrote. “Pre-existing immune memory is typically studied in the context of exposure to related pathogens. Our data provide the basis for considering a broader range of antigen-experiences in the education of the baseline immune responses. Inter-individual differences in the abundance and differentiation states of pre-existing cells resulting from different life experiences may contribute to the heterogeneity of human responses to SARS-CoV-2 and potentially other infections.”

Those “individual differences” in T-cell defenses against the virus could go a long way toward explaining the pattern of death that followed the appearance of the new infectious disease.

As of this writing, the U.S. Centers for Disease Control is reporting 96 percent of the more than 1 million people dead of Covid-19 in the U.S. were 40 years old or older.

T cells have long been known to decline with age, especially among the sedentary. This process is called immunosenescence, and it starts early in life.

As researchers in the United Kingdom observed 15 years ago, “the impact of age-related changes in the immune system was clearly not an issue when the average human life span was approximately 40 years.

“However, over the past 150 years, advances in medical sciences and nutrition have resulted in a dramatic increase in life expectancy to an unprecedented 80 years….Thus, in the absence of any major evolutionary pressure, an immune system that was designed to function for approximately 40 years now has to continue for an additional four decades. Therefore, it is unsurprising that the increased susceptibility to cancers and infections seen in older persons points to severe deficiencies in the immune system.”

Covid-19 has only underlined this susceptibility with age.

Though U.S. death rates start to rise significantly beyond age 40, the bulk of the mortality starts at age 65. Almost 75 percent of the U.S. dead were that age or older, according to the CDC figures.

The mainstream media narrative that says Covid-19 can kill anyone is true; Covid-19 can kill anyone.

But that’s just part of the story.

The reality is that Covid-19 primarily kills the old, and those with chronic illnesses, or what we now term co-morbidities. And it especially kills the old with comorbidities.

Hints from the start

Swedish researchers a year ago suggested that “some sort of pre-immunity” protection against SARS-CoV-2 was the only logical explanation for how the pandemic was playing out in that country, which took a much more relaxed approach to masks and lockdowns than the rest of the world.

A considerable number of Swedes were then dying, but they weren’t dying at anywhere near the rate the pandemic models predicted they should be dying.

Uppsala University critics of Swedish epidemiologist Anders Tengell’s refusal to order the country to lockdown and mask-up used a then-popular model for infection forecasting from the Imperial College London to predict that 80,000 Swedes would die by July (2020) if the country didn’t change its policy.

That didn’t happen.

Two years later, the number of Covid-19 deaths in Sweden has yet to reach 20,000, according to the Worldometer tracker, and the country’s death rate of 1,874 per million shows it doing better against the pandemic than Spain, Italy and France, all of which cracked down hard on their citizens.

Sweden’s death rate is 23 to 50 percent lower than in those countries, but about three times that of Norway, which largely closed its borders, and about two times higher than that of Finland, which instituted an aggressive “track and trace” program to slow the spread of Covid-19 and quickly shutdown restaurants – documented hotbeds for the airborne spread of SARS-CoV-2.

Deutsche Welle (DW), Germany’s international broadcasting service, also noted the Finnish personality might have had something to do with what happened there.

“It may well be that the Finnish comfort zone is slightly bigger than in other European countries,” said Mika Salminen, director of the Finnish Institute for Health and Welfare told the news outlet. “We like to keep 3 feet distance between us and the next person. Otherwise we feel uncomfortable.”

Close contacts between the infected and the uninfected were blamed for much of the early spread of the disease and still are, though it is now accepted that SARS-CoV-2 can be spread broadly through the air in closed spaces.

This has been a problem since the start of the epidemic but has only become more so with the emergency of the Omicron BA.4/5 variants now in circulation.

They are more contagious than the original strain and, according to a peer-reviewed study in Nature, more than four time “more likely to lead to vaccine breakthrough infections” than previous variants.

Boosting defenses

All of this might cause a reasonable person to conclude that public health officials should be putting more emphasis on what people can do to maintain their natural T-cell defenses, but that hasn’t happened.

One of the few things on which the country’s political leaders seem in agreement both right and left is that it’s politically unwise to sends Americans the simple message they need to hear:

“You need to stop stuffing so much food in your face and get off your fat asses and move!”

Diet and exercise do not guarantee improvements in your immune system. Aside from some vaccines which help the immune system target and fight some diseases, researchers still don’t know enough about the immune system to tell anyone how exactly to boost it.

But they do know this: The so-called “sedentary lifestyle”  that has become a norm in the U.S. accelerates the natural and inevitable decay of the immune system.

University of Arizona professor Richard Simpson and colleague Keith Guy appear now to have been prescient when they examined this subject back in 2009 and warned that “the elderly population is at an unprecedented risk of infectious diseases and malignancy due to apparently inevitable age-related declines in immunity.

“As it is generally accepted that middle-aged and elderly individuals who habitually participate in moderate-intensity exercise are less likely to incur an infection than their sedentary counterparts, this review addresses current knowledge on the effects of regular exercise on aspects of adaptive immunity as they relate to the immune response profile.”

They specifically noted the increased “T-cell responsiveness” in the habitually active, but questioned whether exercise begun later in life could help maintain or even reinvigorate the immune system.

The case for “exercise training intervention in previously sedentary elderly to improve similar immune responses is less compelling,” they admitted. “Although this might indicate that exercise has limited immune restorative properties in previously sedentary elderly, there are still relatively few studies that have addressed specific IRP criteria and the large variation in experimental design among the longitudinal studies complicates the juxtaposition of these results.”

Since then, science has learned a little more.

Hungarian scientists who enrolled 29 elderly and sedentary women (mean age 67.03) in a “six-week long functional conditioning gymnastic exercise program” in 2020 found the women strengthened their T-cells and boosted their immune system in general.

“Our findings suggest that exercise-induced changes in the distribution of certain naïve and memory B and T cell subsets as well as in the proportions of regulatory T cells presumably indicate a retuned immune regulation and a restored responsiveness of the immune system,” they wrote when their study was published in the peer-reviewed Frontiers in Immunology in 2021. “Thereby, regular exercise, besides improving physical condition and age-related sarcopenia, may also delay or even reverse immunosenescence therefore can be particularly beneficial in maintaining appropriate immune functions in older ages.”

But it is admittedly easier to sit on the couch and watch TV, piddle away the hours cruising the internet on the computer, and travel everywhere in the comfort of a motor vehicle than to get up and move.

And, with luck, the next miracle of modern medicine will arrive to save you from yourself. If not, well, life is a death sentence for everyone eventually anyway.