We have mainly two immune response instruments in our body. First instrument is antibody. When people think they have had the virus, they undergo a serological test to check for antibodies.
Second, and least known instrument is T lymphocytes. However, there are not enough knowledge about the second instrument. How, white blood cell T-lymphocytes protects us against Covid-19 is not known yet.
The recent pandemic has highlighted the fact that how poorly understood are our body’s immune system.
Antibodies give us protection from future infection. However, with Covid-19, antibodies don’t even last for a month, exposing the already infected people to the virus again.
What about T cells?
One hypothesis is that these T cells might help give people a level of cross-immunity protection from COVID-19 because they “remember” previous infections by other viruses in the same family, four of which cause common colds. A research published in the journal Nature, has tried to shed light on this.
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The research has found that at least a third of adults that had never had COVID-19 have these T cells. The research has concluded that these T cells are most likely to originate from previous infections with endemic coronavirus.
Another study, published in the same journal, in July, had reached the same conclusion.
The latest study builds on research, published in the journal Cell in May by the same team, which detected these SARS-CoV-2 reacting T cells in 40 to 60 per cent of people who had never had COVID-19.
When it comes to getting a vaccine against Covid-19, the great hunt is still on. And all of the vaccines, currently in various development stages, are also trying to get immune response from T cells as well. This is a clear departure from the previous practice when antibodies used to get all the attention.
So far, almost all studies indicate that the level of antibodies for patients who have had COVID-19 subside within weeks.
The latest study draws two conclusions from this:
- Immunity to COVID does not last
- serology tests for antibodies are unable to detect potential immunity
A recent study at Sweden’s Karolinska University Hospital showed that many people with mild or asymptomatic COVID-19 demonstrated a T cell immune response to the virus, even if their antibody test was negative.
Scientists are unanimous that more research is needed to know the immune response generated by the T-cells.
On August 4, a group of 26 researchers, including the lead authors of the “20 to 50 percent” research finding, published a new paper in Science documenting both the origins and the shape of that T-cell cross-reactive immune response.
They found that preexisting T-cell response came primarily via the variety of T-cells called CD4 T-cells, and that this dynamic was consistent with the hypothesis that the mechanism was inherited from previous exposure to a few different “common cold” coronaviruses.