So how could your immune system have reactive T cells if they never had Covid-19? They were “likely acquired from previous endemic coronavirus infections,” the researchers, from various institutions in Germany and the United Kingdom, wrote in the new study. Using this T cell memory from another yet similar infection to respond to a new infection is called “cross reactivity.”
“The big question is … understand what the role of those T cells might be?”
The new study included analysis of blood samples from 18 Covid-19 patients, ages 21 to 81, and healthy donors, ages 20 to 64, based in Germany. The study found that coronavirus-reactive T cells were detected in 83% of Covid-19 patients.
While the researchers also found preexisting cross-reactive T cells in healthy donors, they wrote in the study that the impact those cells could have on the outcome of Covid-19 disease is still unknown.
“It appears in this study that there is a significant proportion of individuals who have this cross-reactive T-cell immunity against other coronavirus infections that may have some impact on how they are doing with the new coronavirus. I think the big question is trying to skip from the fact that they have these T cells to understand what the role of those T cells might be, “Adalja said.
“We know, for example, that children and younger adults are relatively safe from the serious consequences of this disease, and I think one hypothesis could be that existing pre-existing T cells may be much more numerous or more active in the younger age. ” cohorts than older cohorts, “said Adalja.
“And if you could compare people with severe and mild diseases and try to look at T cells in those people and say, ‘Are people with severe disease less likely to have cross-reactive T cells compared to people who do they have mild disease? more cross reactive T cells? I think there is a biological possibility of that hypothesis, “he said. “However, it is clear that the presence of T cells does not prevent people from becoming infected, but does it modulate the severity of the infection? That seems to be the case.”
Until now, during the coronavirus pandemic, much attention has been paid to Covid-19 antibodies and their role in developing immunity against the disease.
“Here’s a study that suggests that there may actually be some cross-reactivity, some pump priming if you like, with the normal conventional coronaviruses that cause colds in humans and there may be some cross-reactivity with the Covid virus that is causing so much damage. That in itself is intriguing because we had thought from the antibody perspective that there wasn’t much crossover at all, “Schaffner said.
“It is not entirely surprising because they are all members of a family. It is as if they are cousins of the same family,” he said. “Now we have to see if this has any impact on clinical practice … Does it make the person infected with Covid more or less likely to develop a disease? And does it have any implications for the vaccine? Development?”
‘Almost everyone in the world has had an encounter with a coronavirus’
Adalja added that he was not surprised to see this cross-reactivity of T cells in study participants who had not been exposed to the new coronavirus, called SARS-CoV-2.
“SARS-CoV-2 is the seventh human coronavirus ever discovered, and four of the human coronaviruses are what we call community-acquired coronaviruses, and together those four are responsible for 25% of our common colds,” said Adalja . “Almost everyone in the world has had an encounter with a coronavirus, and since they are all part of the same family, some cross-reaction immunity develops.”
The new Nature study is not the only article suggesting a certain level of pre-existing immunity among some people to the new coronavirus.
Sette and Crotty wrote that “it has now been established that the pre-existing immune reactivity of SARS-CoV-2 exists to some extent in the general population. It is presumed, but not yet proven, that this could be due to immunity to the” cold common coronavirus.
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