How the Aging Immune System Makes Older People Vulnerable to Covid-19
As we age, the immune system begins to shift into a heightened state of alert, dialing up inflammation and running out of certain immune cells.
Covid-19 patients who are 80 or older are hundreds of times more likely to die than those under 40.
That’s partly because they are more likely to have underlying conditions — like diabetes and lung disease — that seem to make the body more vulnerable to Covid-19.
But some scientists suggest another likely, if underappreciated, driver of this increased risk: the aging immune system.
The changes that ripple through our network of immune cells as the decades pass are complex, resulting in an overreaction here, a delayed response there and over all, a strangely altered landscape of immunity.
Scientists who study the aging immune system say that understanding it may lead not only to a clearer sense of how age is connected to disease vulnerability, but to better strategies for vaccines and treatments for Covid-19.
“I felt like I was shouting at people, ‘This is what’s going on!’ but no one was listening,” said Arne Akbar, a professor of immunology at University College London who recently published an article in the journal Science explaining the state of research on the aging immune system.
When a virus infiltrates the body, cells in the first line of defense act swiftly and violently — sending out alerts and instructions to other cells, and provoking inflammation to start knocking down the virus.
The “innate” immune system, as it’s called, also happens to be responsible for cleaning up damaged cells, misfolded proteins and other detritus in the body, even when there’s no infection to fight.
In older people, such waste seems to outrun the immune system’s ability to clear it, however, said Dr. Eric Verdin, the chief executive of the Buck Institute for Research on Aging in Novato, Calif. The innate immune system grows overwhelmed, and slides into a constant state of alert and inflammation.
At same time, elderly cells in tissues throughout the body are thought to change with age, releasing inflammatory substances of their own.
“They are not just benign, like old nice grandparents,” Dr. Akbar said. “They’re actually very cantankerous.”
As a result, even perfectly healthy 65-year-olds usually have higher levels of immune proteins, like cytokines, involved in inflammation than younger people do. This heightened state of chronic inflammation, sometimes called “inflammaging,” is linked to frailty — older adults with higher levels of it may be more fragile and less mobile.
