Antibodies have become a familiar word in the pandemic era, perhaps suggesting they’re the best hope for keeping the deadly coronavirus at bay. But when crucial vaccine data was released this week, the spotlight panned to an unsung immune player: T cells.
Thrust into focus by recent studies, T cells are a reminder that the body’s defenses rely on more than one weapon. Much of the immune response to Covid-19 is still a mystery -- especially after researchers revealed that the more lauded antibodies
“Antibodies are only a tiny part of the picture,” said
As the pandemic took the world by storm, scientists first focused on antibodies -- proteins that stick to and disable foreign invaders -- because eliciting them is the basis for most successful vaccines. The immune proteins are also easier to measure than T cells and can be used to gauge prior infection.
The study showing they wane quickly in patients with mild disease dealt a blow to hopes that antibodies will provide some lasting form of immunity.
By contrast, T cells can kill virus-infected cells, remember past diseases for decades, and rouse fresh antibody soldiers long after the first has left the battlefield. People infected with another coronavirus that was responsible for the SARS epidemic in 2003, for example, still have a T-cell response to the disease
That suggests T cells may still, at least hypothetically, be ready to protect SARS survivors against the infection almost two decades later, and might bolster their defense against Covid-19, Griffin said. “They might have a slightly milder or shorter duration in terms of the course of their illness, but I certainly wouldn’t think that that would be protective, unfortunately,” he said.
One study found that some patients with no symptoms of Covid-19 had
More research is needed to determine whether pre-existing T cells that cross-react with the SARS-CoV-2 virus may explain why some COVID patients are barely affected while others get very sick and even die. What’s clear is that a balance of both antibodies and T cells is necessary for optimal defense, according to Griffin.
So-called helper T cells and memory T and B cells can prime antibodies to respond to a subsequent infection before it causes severe symptoms, said Smith, who is studying the immune response to the SARS-CoV-2 virus.
Like other coronaviruses that cause the common cold, the virus may have a way of evading antibodies, leading to reinfection, Smith said. “But, there’s enough cellular immunity to put a dampener on any severe symptoms.”
If could be that T cells are what ultimately subdue and blunt the pandemic virus that’s killed more than 600,000 people in less than seven months.
“If we can’t eradicate it, does it end up as a kind of a circulating virus, another cold virus?” Smith said. “I’m not sure, but it’s interesting.”